Radiation-curable, optical fiber primary coating system

ABSTRACT

Optical fiber primary coating systems are disclosed having excellent ribbon stripping and adhesion behavior. The coatings are radiation-curable. The excellent stripping and adhesion behavior can be inner piramry coating composition having a slip enhancing component and a high modulus outer primary coating composition. Combination of means can be employed. Stripping behavior can be measured by crack propagation and fiber friction measurements.

FIELD OF THE INVENTION

[0001] The invention relates to radiation-curable, optical fiber coatingsystems comprising an inner and an outer primary coating compositions.The invention also relates to coated optical fibers and optical fiberassemblies. More particularly, the invention relates to aradiation-curable, optical fiber coating system that provides improvedstrip cleanliness and optical fibers coated with the coating system,ribbon assemblies comprising such coated optical fibers and methods ofmaking and forming the same.

BACKGROUND OF THE INVENTION

[0002] Optical fiber coating systems commonly comprise two coatingcompositions. The first coating composition contacts the glass surfaceand is called the inner primary coating. The second coating compositionis designed to overlay the inner primary coating and is called the outerprimary coating.

[0003] The inner primary coating is usually a soft coating having a lowglass transition temperature (hereinafter “Tg”), to provide resistanceto microbending. Microbending can lead to attenuation of the signaltransmission capability of the coated optical glass fiber and istherefore undesirable. The outer primary coating is typically a hardercoating providing desired resistance to handling forces, such as thoseencountered when the coated fiber is cabled.

[0004] For the purpose of multi-channel transmission, optical fiberassemblies containing a plurality of coated optical fibers have beenused. Examples of optical fiber assemblies include ribbon assemblies andcables. A typical optical fiber assembly is made of a plurality ofcoated optical fibers which are bonded together in a matrix material.For example, the matrix material can encase the optical fibers, or thematrix material can edge-bond the optical fibers together.

[0005] Optical fiber assemblies provide a modular design whichsimplifies the installation and maintenance of optical fibers byeliminating the need to handle individual optical fibers.

[0006] Coated optical fibers for use in optical fiber assemblies areusually coated with an outer colored layer, called an ink coating, oralternatively a colorant is added to the outer primary coating tofacilitate identification of the individual coated optical glass fibers.Such ink coatings and colored outer primary coatings are well known inthe art. Thus, the matrix material which binds the coated optical fiberstogether contacts the outer ink layer if present, or the colored outerprimary coating.

[0007] When a single optical fiber of the assembly is to be fusionconnected with another optical fiber, or with a connector, an end partof the matrix layer is required to be stripped away from the opticalfiber. A common method for practicing ribbon stripping at a terminus ofthe ribbon assembly is to use a heated stripping tool. Such a toolconsists of two plates provided with heating means for heating theplates to about 90 to about 120 C. An end section of the ribbon assemblyis pinched between the two heated plates and the heat of the toolsoftens the matrix material and the primary coatings prior to and duringthe stripping procedure.

[0008] Ideally, the primary coatings on the coated optical fibers, andthe ink coating if present, are removed simultaneously with the matrixmaterial to provide bare portions on the surface of the optical fibers(hereinafter referred to as “ribbon stripping”). In ribbon stripping,the matrix material, primary coatings, and ink coating, are desirablyremoved as a cohesive unit to provide a clean, bare optical glass fiberwhich is substantially free of residue. Any residue can interfere withthe optical glass fiber ribbon mass fusion splicing operation, andtherefore is presently removed by wiping with a solvent prior tosplicing. However, the solvent wipe can cause abrasion sites on the bareoptical fiber, thus compromising the integrity of the connection. Manyattempts have been made increase the strip cleanliness of the ribbonassemblies by adding adhesion reducing additives to the inner primarycoating which results in systems with little improvement in the stripcleanliness or system with insufficient adhesion. The ability to produceribbon assemblies that can be stripped to provide clean, residue-free,bare optical glass fibers without unduly sacrificing other desirable orrequired properties of the primary coatings continues to challenge theindustry.

[0009] There are many test methods which may be used to determine theperformance of a ribbon assembly during ribbon stripping. An example ofa suitable test method for determining the stripping performance of aribbon is disclosed in the article by Mills, G., “Testing of 4- and8-fiber ribbon strippability”, 472 International Wire & Cable SymposiumProceedings (1992), the complete disclosure of which is incorporatedherein by reference.

[0010] Many attempts have been made to understand the problemsassociated with ribbon stripping and to find a solution to increaseribbon stripping performance. The following publications attempt toexplain and solve the problems associated with ribbon stripping: K. W.Jackson, et. al., “The Effect of Fiber Ribbon Component Materials onMechanical and Environmental Performance”, 28 International Wire &Symposium Proceedings (1993); H. C. Chandon, et. al., “Fiber ProtectiveDesign for Evolving Telecommunication Applications”, International Wire& Symposium Proceedings (1992); J. R. Toler, et. al., “Factors AffectingMechanical Stripping of Polymer Coatings From Optical Fibers”,International Wire & Cable Symposium Proceedings (1989); and W.Griffioen, “Strippability of Optical Fibers”, EFOC & N, Eleventh AnnualConference, Hague (1993).

[0011] The ability of a ribbon assembly to ribbon strip cleanly so as toprovide bare optical glass fibers that are substantially free of residuewas heretofore unpredictable and the factors affecting ribbon strippingnot fully understood. Accordingly, there is a need for an optical fiber,radiation-curable coating composition system that improves thestrippability of optical fiber ribbons.

SUMMARY OF THE INVENTION

[0012] It is an objective of the present invention to provide aradiation-curable, optical fiber primary coating system comprising aninner primary coating composition and a, colored or non-colored, outerprimary coating composition that imparts improved ribbon stripping to aribbon assembly, when incorporated therein.

[0013] It is another objective of the present invention to provide acoated optical fiber having a coating such that when it is incorporatedinto a ribbon assembly the ribbon assembly achieves better stripcleanliness.

[0014] It is another objective of the present invention to provide aribbon assembly having improved ribbon stripping capabilities.

[0015] It is still a further objective of the present invention toprovide a method of preparing a radiation-curable, optical fiber coatingsystem comprising an inner primary coating composition and an outerprimary coating composition that imparts improved ribbon stripping to aribbon assembly, when incorporated therein.

[0016] Surprisingly, the above objects and other objects are and havebeen obtained by the following. The present invention provides aradiation-curable, optical fiber primary coating system having; i) aradiation-curable inner primary coating composition comprising at leastone slip enhancing component wherein said composition, after cure, iscapable of sufficiently adhering to an optical fiber so as to preventdelamination in the presence of moisture and during handling, and ii) aradiation-curable outer primary coating composition that, upon cure, hasa secant modulus of 1000 MPa (when measured on Mylar). Suitable slipenhancing components including, for example:

[0017] a. an oligomer comprising at least one slip agent moiety and/or acomposite oligomer comprising at least one glass coupling moiety, atleast one slip agent moiety, and at least one radiation-curable moietycapable of polymerizing under the influence of radiation;

[0018] b. a soluble wax that is soluble in said inner primary coatingcomposition and/or a solid lubricant;

[0019] c. a radiation-curable silicone oligomer and/or a siliconecompound which may be either non-radiation-curable or radiation-curableand/or mixtures thereof;

[0020] d. a silicone compound containing at least one radiation-curablefunctional group bound near a terminus of said compound;

[0021] e. a fluorinated component selected from the group consisting ofa radiation-curable fluorinated oligomer, a radiation-curablefluorinated monomer, a non-radiation curable fluorinated compound ormixtures thereof;

[0022] f. a radiation-curable oligomer comprising at least one terminallinear moiety and/or at least one substantially linear radiation-curableoligomer;

[0023] g. a low-urethane oligomer wherein the calculated molecularweight concentration of said urethane groups in said oligomer is about4% by weight or less, based on the total calculated molecular weight ofthe oligomer;

[0024] h. a radiation-curable oligomer having a polymeric backbone thathas a molecular weight of at least about 2000, preferably more than3100;

[0025] i. a radiation-curable oligomer and/or monomer diluent having ahigh aromatic content; and/or

[0026] j. other slip enhancing additives and/or components discussed inapplicants concurrently pending U.S. application Ser. No. 09/035,771,the entire disclosure of which is hereby incorporated by reference.

[0027] Also provided by the present invention is a coated optical fibercoated with a radiation-curable, optical fiber primary coating systemdiscussed herein, a ribbon assembly comprising: a plurality of opticalfibers, at least one optical fiber coated with a radiation-curable,optical fiber primary coating system discussed herein, and optionally anink coating; and a matrix material bonding said plurality of coatedoptical fibers together; and processes for making such coated opticalfibers and ribbon assemblies.

[0028] Other objects and advantages of the present invention will becomemore apparent to those persons having ordinary skill in the art to whichthe present invention pertains from the following description taken inconjunction with the accompanying drawings.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0029] The present invention is direct to radiation-curable, opticalfiber primary coating systems (optical fibers coated with a primarycoating system, and ribbon assemblies comprising such coated opticalfibers) that provide improved ribbon stripping (i.e., when incorporatedinto a ribbon assembly enable the cured coatings, matrix materials andoptional inks coating materials to strip relatively cleanly from theoptical fiber). The primary coating systems of the present inventioncombines a radiation-curable inner primary coating having a slipenhancing component with a relatively high secant modulus outer primarycoating to achieve improved ribbon stripping. The present inventionprovides a radiation-curable, optical fiber coating system comprising aradiation-curable inner primary coating composition and aradiation-curable outer primary coating composition. The coatingcompositions according to the present invention include those formulatedfrom (A) a oligomer (often referred to as a pre-polymer) system, (B) amonomer diluent system, (C) an optional photoinitiator system, and (D)additives. Background teachings on how to formulate and applyradiation-curable compositions for fiber optic materials can be foundin, for example, U.S. Pat. Nos. 5,384,342; 5,456,984; 5,596,669;5,336,563; 5,093,386; 4,716,209; 4,624,994; 4,572,610; and 4,472,019,which are hereby incorporated in their entirety by reference.

[0030] For this invention, “pre-mixture ingredients” means that whenformulating a radiation-curable composition from its ingredients, someinteraction or reaction of the ingredients is possible in some casesafter mixing. However, pre-mixture ingredient refers to the identity ofthe ingredient before any such interaction or reaction of theingredients might occur after mixing.

[0031] Also, for this invention, “(meth)acrylate” means acrylate,methacrylate, or a mixture thereof. For this invention, “pre-polymer”and “oligomer” have equivalent meaning.

[0032] (A) The Oligomer System

[0033] In this invention, the pre-polymer or oligomer system comprisesone or more radiation-curable oligomers. In general, an oligomer systemis first prepared, optionally in the presence of a monomer diluent.Then, the oligomer formulation is further formulated by mixing withother ingredients such as monomer diluents, photoinitiator, andadditives. If multiple oligomers are desired, individual oligomers canbe synthesized separately, and then mixed, or they can be synthesizedtogether in a single, one-pot synthesis. In either case, the synthesisof oligomers often produces a statistical distribution of differenttypes of oligomers which can be represented by idealized structures.

[0034] If some ingredients from the monomer diluent system (see below)are present during oligomer synthesis, they are not considered part ofthe pre-polymer system because, in general, monomer diluent does notreact substantially during oligomer preparation and merely functions asa solvent for oligomer synthesis. In general, a monomer diluent can bedistinguished from an oligomer because it will have a lower molecularweight than an oligomer, and will serve to decrease the viscosity of anoligomer. However, some monomer diluents can have repeating units suchas repeating alkoxy units. However, for this invention, if the diluentfunctions to decrease the viscosity of the oligomer, then it is a calleda diluent rather than an oligomer.

[0035] The amount of the oligomer system (A) can be, for example, about10 wt. % to about 90 wt. %, and preferably, between about 20 wt. % toabout 80 wt. %, and more preferably, about 30 wt. % to about 70 wt. %.Preferably, the oligomer amount is about 50 wt. %. If more than oneoligomer is present, then the wt. % of each oligomer is added.

[0036] Radiation-curable oligomers can comprise one or moreradiation-curable end groups and an oligomer backbone. The end-groupprovides a cure mechanism, whereas the backbone provides suitablemechanical properties upon cure. In addition, the oligomer can compriseone or more linking groups such as a urethane- or urea-containing moietywhich further can improve the mechanical performance of curedcompositions. The linking groups can link an oligomeric backbone moietyto the radiation-curable end-group, or link oligomeric backbone moietiesto themselves. Hence, for example, radiation-curable oligomers can beprepared from three basic components (backbone, linking, andradiation-curable components) and can be represented by structures suchas, for example:

R-[L-B]_(x)-L-R

[0037] where R is a radiation-curable group, L is a linking group, and Bis a backbone moiety. The variable x indicates the number of backbonemoieties per oligomer molecule. This value X can be controlled by, forexample, control of the reaction stoichiometry during oligomersynthesis. Typically, X is designed to be 1. In this representation, Land B are difunctional moieties, but oligomers can also be prepared fromtri- and higher functional L and B moieties to provide branching. In thepresent invention, branching points in the oligomer are preferablypresent, and preferably result from use of at least some tri-functionalgroups L. Then, for example, an oligomer can also be represented by:

(R)₂-L-B-L-(R)₂

[0038] In particular, typical radiation-curable urethane acrylateoligomers according to the present invention are prepared from (i) atleast one ingredient which reacts to provide the radiation-curableacrylate group R, (ii) at least one ingredient which reacts to providethe urethane linking group L, and (iii) at least one ingredient whichreacts to provide the backbone B. Different urethane acrylate oligomersynthetic strategies are disclosed in, for example, U.S. Pat. No.5,093,386, which is hereby incorporated by reference. Other syntheticmethods, however, may be used to prepare equivalent structures. Thesemethods may be adapted by methods known in the art to provide urealinkages, methacrylate linkages, and other common types of linkagesfound in radiation-curable oligomers.

[0039] The radiation-curable oligomer can cure by reaction of itsradiation-curable groups, R, via a free-radical mechanism or by cationicmechanism. A free-radical cure, however, is preferred. Ethylenicallyunsaturated groups are preferred. Exemplary radiation-curable groupsinclude (meth)acrylate, vinyl ether, vinyl, acrylamide, maleate,fumarate, and the like. The radiation-curable vinyl group canparticipate in thiol-ene or amine-ene cure. Most preferably, theradiation-curable group is an acrylate if fast cure speed is desired.

[0040] Preferably, the oligomer comprises at least two radiation-curablegroups, and preferably, at least two ethylenically unsaturated groups.The oligomer, for example, can comprise two, three, or fourradiation-curable groups which are all preferably ethylenicallyunsaturated groups. There is no strict upper limit on the number ofradiation-curable groups per oligomer, but in general, the number ofradiation-curable groups is less than 10, and preferably, less than 8.

[0041] The oligomer can comprise copolymeric structures including randomand block copolymeric structures. Methods known in the art can be usedto prepare such copolymeric structures. For example, backbone moietiescan be copolymeric. Also, a one-pot synthesis of multiple oligomers canbe executed with use of multiple backbone moieties. Using multiplebackbone moieties can yield at least some block copolymeric oligomers inthe pre-polymer system. Formulation design of copolymeric oligomers canresult in a better balance of properties and provide synergisticeffects, which usually is crucial for fiber optic materials. Inaddition, oligomer blends or mixtures can be used to balance propertiesand provide synergistic effects.

[0042] For processing reasons, it is important to control the oligomersystem's viscosity and flow behavior. For practical reasons, oligomersshould be easy to remove from the reactors and flasks in which they aresynthesized. If viscosity is too high, it will be difficult to processthe oligomer system during formulation, even with some monomer diluentpresent.

[0043] If an oligomeric polyether diol is used, the polyether mayinclude, for example, substantially non-crystalline polyethers. Theoligomer may include polyethers comprising repeating units of one ormore of the following monomer units:

[0044] —O—CH₂—CH₂—

[0045] —O—CH₂—CH₂—CH₂—

[0046] —O—CH₂—CH(CH₃)—

[0047] —O—CH₂—CH₂—CH₂—CH₂—

[0048] —O—CH₂—CH(CH₃)—CH₂—

[0049] —O—CH₂—CH(CH)₃—CH₂—CH₂—

[0050] —O—CH(CH₃)—CH₂—CH₂—CH₂—.

[0051] —O—CH(CH₂CH₃)—CH₂—.

[0052] —O—CH₂—C(CH₃)(CH₃)—, and the like.

[0053] An example of a polyether polyol that can be used is thepolymerization product of (i) tetrahydrofuran, or (ii) a mixture of 20percent by weight of 3-methyltetrahydrofuran and 80 percent by weight oftetrahydrofuran, both of which have undergone a ring openingpolymerization. This latter polyether copolymer contains both branchedand non-branched oxyalkylene repeating units and is marketed as PTGL1000 (Hodogaya Chemical Company of Japan). Another example of apolyether in this series which can be used is PTGL 2000. (HodogayaChemical Company). Butyleneoxy repeat units are preferred to impartflexibility to one oligomer in particular and the pre-polymer system ingeneral.

[0054] If a polyolefin diol is used, the polyolefin is preferably alinear or branched hydrocarbon containing a plurality of hydroxyl endgroups. Fully saturated, for example, hydrogenated hydrocarbons, arepreferred because the long term stability of the cured coating increasesas the degree of unsaturation decreases. Examples of hydrocarbon diolsinclude, for example, hydroxyl-terminated, fully or partiallyhydrogenated 1,2-polybutadiene; 1,4- and 1,2-polybutadiene copolymers,1,2-polybutadiene-ethylene or -propylene copolymers, polyisobutylenepolyol; mixtures thereof, and the like.

[0055] Other suitable oligomers may include polyester oligomers,polycarbonates oligomers, mixtures of any of the aforementioned oligomertypes and the like.

[0056] The linking group of the oligomer can be a urethane or ureagroup, and preferably is a urethane group. It is well-known in the artthat urethane linkages can be formed by reaction of a polyfunctionalisocyanate with a hydroxy compound including a hydroxy-containingbackbone component or a hydroxy-containing radiation-curable component.

[0057] Polyfunctional isocyanates include diisocyanates, triisocyanates,and higher order polyisocyanates which can provide the linking group. Asknown in the art, isocyanate compounds can be trimerized to formisocyanurate compounds which can provide the linking group. Hence,polyisocyanate compounds can be oligomerized or polymerized to formhigher order polyisocyanates comprising isocyanurate group. Isocyanuratecompounds are a preferred example of how to provide a cyclic grouphaving the capacity to hydrogen bond.

[0058] Generally, the compound providing a radiation-curable terminus tothe oligomer contains a functional group which can polymerize under theinfluence of actinic radiation and a functional group which can reactwith the diisocyanate. Hydroxy functional ethylenically unsaturatedmonomers are preferred. More preferably, the hydroxy functionalethylenically unsaturated monomer contains acrylate, methacrylate, vinylether, maleate or fumarate functionality.

[0059] In the reaction between hydroxy group of the compound providingthe terminus and isocyanate groups of compound providing the linkingsites, it is preferred to employ a stoichiometric balance betweenhydroxy and isocyanate functionality and to maintain the reactiontemperature of at least 25° C. The hydroxy functionality should besubstantially consumed. The hydroxy functional ethylenically unsaturatedmonomer attaches to the isocyanate via a urethane linkage. Monomershaving (meth)acrylate functional groups include, for example, hydroxyfunctional (meth)acrylates such as 2-hydroxyethyl acrylate,2-hydroxypropyl acrylate, methacrylate analogs, and the like. Monomershaving vinyl ether functional groups include, for example,4-hydroxybutyl vinyl ether, and triethylene glycol monovinyl ether.Monomers having maleate functional groups include, for example, maleicacid and hydroxy functional maleates.

[0060] There is no particular limitation on the molecular weight of theoligomer, but the number average molecular weight of the oligomer ingeneral can be less than about 25,000 g/mol, and preferably, less thanabout 10,000 g/mol, and more preferably, less than about 5,000 g/mol.Molecular weight is preferably greater than about 500 g/mol.

[0061] (B) The Monomer Diluent System

[0062] The compositions according to the invention also comprises amonomer, or reactive, diluent system which comprise at least one monomerdiluent. The reactive diluent can be used to adjust the viscosity of thecoating composition. Thus, the reactive diluent can be a low viscositymonomer containing at least one functional group capable ofpolymerization when exposed to actinic radiation.

[0063] The reactive diluent is preferably added in such an amount thatthe viscosity of the coating composition is in the range of about 1,000to about 10,000 mPa.s.

[0064] Suitable amounts of the reactive diluent have been found to beabout 10 wt % to about 90 wt %, and more preferably about 20 wt. % toabout 80 wt. %, and more preferably, about 30 wt. % to about 70 wt. %.

[0065] A monomer diluent preferably has a molecular weight of not morethan about 550 or a viscosity at room temperature of not more than about300 mPa.s (measured as 100% diluent).

[0066] The radiation-curable functional group present on the reactivediluent may be of the same nature as that used in the radiation-curableoligomer. Preferably, the radiation-curable functional group present inthe reactive diluent is capable of copolymerizing with theradiation-curable functional group present on the radiation-curableoligomer. Ethylenic unsaturation is preferred. In particular, acrylateunsaturation is preferred.

[0067] Preferably, the reactive diluent system comprises a monomer ormonomers having an acrylate or vinyl ether functionality and an C₄-C₂₀alkyl or polyether moiety. Examples of such reactive diluents includehexylacrylate, 2-ethylhexylacrylate, isobornylacrylate, decylacrylate,laurylacrylate, stearylacrylate, ethoxyethoxy-ethylacrylate,laurylvinylether, 2-ethylhexylvinyl ether, N-vinyl formamide, isodecylacrylate, isooctyl acrylate, vinylcaprolactam, N-vinylpyrrolidone andthe like.

[0068] Another type of reactive diluent is a compound comprising anaromatic group. Examples of diluents having an aromatic group include:

[0069] ethyleneglycolphenyletheracrylate,

[0070] polyethyleneglycolphenyletheracrylate,

[0071] polypropyleneglycolphenyletheracrylate, and

[0072] alkyl-substituted phenyl derivatives of the above monomers, suchas

[0073] polyethyleneglycolnonylphenyletheracrylate.

[0074] Furthermore, a reactive diluent can contain two groups capable ofpolymerization using actinic radiation. A diluent having three or moreof such reactive groups can be present as well. Examples of suchmonomers include:

[0075] C₂-C₁₈ hydrocarbondioldiacrylates,

[0076] C₄-C₁₈ hydrocarbondivinylethers,

[0077] C₃-C₁₈ hydrocarbontrioltriacrylates,

[0078] the polyether analogs thereof, and the like, such as

[0079] 1,6-hexanedioldiacrylate,

[0080] trimethylolpropanetriacrylate,

[0081] hexanedioldivinylether,

[0082] triethyleneglycoldiacrylate,

[0083] pentaeritritoltriacrylate,

[0084] tripropyleneglycol diacrylate

[0085] alkoxylated bisphenol A diacrylate.

[0086] Preferably, the oligomer and the reactive diluent each contain anacrylate group as a radiation-curable group.

[0087] (C) The Optional Photoinitiator System

[0088] The composition may optionally further comprise at least onephotoinitiator. Photoinitiator is required for a fast UV cure but may beomitted for electron beam cure. Conventional photoinitiators can beused. Examples include benzophenones, acetophenone derivatives, such asalpha-hydroxyalkylphenylketones, benzoin alkyl ethers and benzil ketals,monoacylphosphine oxides, and bisacylphosphine oxides. A preferredphotoinitiator is 1-hydroxycyclohexylphenylketone (Irgacure 184, CibaGeigy).

[0089] Often mixtures of photoinitiators provide a suitable balance ofproperties.

[0090] The amount of photoinitiator system is not particularly limitedbut will be effective to provide fast cure speed, reasonable cost, goodsurface and through cure, and lack of yellowing upon aging. Typicalamounts can be, for example, about 0.3 wt. % to about 10 wt. %, andpreferably, about 1 wt. % to about 5 wt. %.

[0091] (D) Additives

[0092] Conventional additives can be used in effective amounts. Forexample, additives such as stabilizers to prevent gellation, UVscreening compounds, leveling agents, polymerization inhibitors, lightstabilizers, chain transfer agents, colorants including pigments anddyes, plasticizers, fillers, wetting improvers, preservatives, and thelike. Other polymers and oligomers can be added to the compositions.Moisture content in the coatings is preferably minimized.

[0093] Preferred inner primary coating compositions of the primarycoating system of the present invention comprise in place of or inaddition to the above-noted components a sufficient amount of one ormore slip enhancing components such that after cure the composition hasin addition to:

[0094] i) a glass transition temperature below 0° C., preferably below−10° C., more preferably below −20° C.; and

[0095] ii) sufficient adhesion to said glass fiber to preventdelamination in the presence of moisture, preferably, an adhesion of atleast 5 g/in when conditioned at 95% (RH);

[0096] a fiber friction value of less than 40 g/mm, preferably less than30 g/mm, more preferably less than 20 g/mm, most preferably greater than10 g/mm and a crack propagation of greater than 0.7 mm at 90° C.,preferably greater than 1.0 mm, more preferably greater than 1.5 mm, andmost preferably, greater than 2 mm at the desired/design ribbonstripping temperature, of for instance 90° C.

[0097] Preferred outer primary coating compositions of the primarycoating system of the present invention which may be colored ornon-colored include compositions generally formulated from components asset forth herein that have, after cure, a secant modulus of greater than1000 MPa, preferably greater than 1050 MPa, and more preferably greaterthan 1100 MPa at 23° C. and a glass transition temperature of above 40°C., preferably above 50° C.

[0098] (E) Slip Enhancing Component

[0099] 1) Composite Oligomer

[0100] A suitable slip enhancing component of the present inventionincludes a composite oligomer that can be used to adjust the fiberfriction between the inner primary coating and the surface of theoptical glass fiber. The composite oligomer comprises at least one glasscoupling moiety, at least one slip agent moiety, and/or at least oneradiation-curable moiety. Preferably, the composite oligomer willcomprise at least two different types of these moieties, for example, atleast one a slip agent moiety and at least one radiation-curable moiety,more preferably the composite oligomer will comprise at least one ofeach of these three types of moieties. Preferably, the various moietiesof the composite oligomer are covalently bonded together. Linkage ofthese moieties can be direct so that there are no intermediate linkinggroups between the oligomer and the moiety. Alternatively, however, thelinkage can be indirect by using intermediate linking groups.

[0101] A variety of glass coupling, slip agent, and radiation-curablemoieties are known in the art. The present invention can be practicedwith use of various embodiments using different combinations of thesemoieties to produce a composite oligomer. A person skilled in the artwill easily be able to prepare combinations of these various moietiesfrom the present disclosure and general knowledge in the art.

[0102] Radiation-curing can occur by reaction of the compositeoligomer's radiation-curable moieties with themselves and/or withradiation-curable moieties bound to other components of a formulation.In general, curing of the composite oligomer occurs in concert withother radiation-curable components. The inner primary compositionscomprising a composite oligomer are preferably directed to reactionswherein the radiation-curable moiety reacts not with the glass couplingor slip agent moieties. For example, although the glass coupling moietywill be reactive, and is often sensitive to hydrolysis and condensationreactions, these types of reactions are not the preferred curemechanism.

[0103] The molecular weight of the composite oligomer is not limited. Ingeneral, however, the molecular weight of the composite oligomer in itsuncured state is usually between about 200 and about 10,000, preferablybetween about 500 and about 5,000.

[0104] There is no particular limitation on the molecular architectureof the composite oligomer, although linear or substantially linearoligomeric structures are preferred over other useful non-linear,cyclic, or branched structures. A substantially linear structure meansthat there is a single, dominant linear oligomeric backbone which is“capped” at the two ends of the backbone. The amount of branching unitsin the backbone is generally less than about 10 mole %, and preferably,less than about 5 mole %. The linear backbone may contain one or moretypes of repeat units, although preferably, one major type of repeatunit is used. Nevertheless, block or random copolymeric structures canbe used if necessary. With a substantially linear backbone, the numberof branch points in the backbone will be kept to a minimum, andpreferably, will not be used. Synthetic simplicity in the oligomerstructure is preferred to the extent that cost-performance can beachieved.

[0105] The term “glass coupling moiety” is understood to mean afunctional group which is known or has the ability to improve adhesionto an inorganic surface and in particular, a glass surface. Preferably,the glass coupling moiety includes groups that are known to covalentlybond with an inorganic material, particularly as a result of ahydrolysis and/or condensation reaction. Suitable glass couplingmoieties may include those derived from conventional coupling agentsincluding conventional silane coupling agents disclosed in E. P.Plueddemann's Silane Coupling Agents, Plenum Press (1982), the completedisclosure of which is hereby incorporated by reference; non-silanecoupling agents, for example, chromium, orthosilicate, inorganic ester,titanium, and zirconium systems. Although the present invention ispreferably practiced with use of silane glass coupling moieties, theinvention is not so restricted, and a person skilled in the art isenabled by the present disclosure to use these other systems as well.

[0106] In the present invention, the glass coupling moieties may bederived from these conventional coupling agents which are covalentlyincorporated into the composite oligomer in a manner which preservestheir coupling function to the inorganic surface. In a preferredembodiment, for example, the organic component of a conventionalcoupling agent is linked covalently, either directly or indirectly, withthe composite oligomer which additionally comprises slip agent andradiation-curable moieties. After this linkage, the glass couplingmoiety will still have its inorganic component effective for bondingwith the inorganic surface or at the inorganic-organic interface.However, the invention is not so limited, and the glass coupling moietyis not necessarily linked to the composite oligomer by reaction of theorganic functional group of a conventional coupling agent.

[0107] Silane coupling moieties are preferred. Silane coupling moietieshaving at least one hydrolyzable “—Si—O—R” linkage are particularlypreferred. Even more preferred are silane coupling moieties representedby the following formula:

—Si(OR)₃

[0108] where R represents a C₁-C₄ alkyl group, preferably methyl orethyl, which imparts at least some hydrolyzability to the silane.

[0109] Common organic functionalities of the silane coupling agentsinclude, for example, amino, epoxy, vinyl, methacryloxy, isocyanato,mercapto, polysulfide, and ureido. Using synthetic methods known in theart, the organic functionality can be reacted with the oligomer to yielda covalent linkage between the glass coupling moiety and the oligomer.In a preferred embodiment, for example, mercaptopropyl silane is linkedwith an oligomer containing an isocyanate group to form a thiourethaneadduct between the mercapto group and the isocyanate group. Although astrong linkage is preferred, the present invention encompasses thepossibility that although a covalent linkage is formed, the covalentlinkage may not be strong and may, for example, be sensitive todisruption with the application of heat. However, as long as the glasscoupling moiety produces the desirable effect of promoting adhesion, thecovalent linkage is sufficient. If necessary, catalysts may be used topromote linkage formation.

[0110] Slip agent moiety of the composite oligomer do not substantiallyaffect the adhesion of the inner primary coating to the surface of theoptical glass fiber. Instead, the slip agent moiety is intended toreduce the sliding force of the inner primary coating against thesurface of the optical glass fiber, once the bonds between the surfaceof the optical glass fiber and inner primary coating are broken (i.e.after the inner primary coating has been delaminated).

[0111] Slip agents are known in the art as, among other things, release,antiblocking, antistick, and parting agents. Slip agents are commonlyoligomeric or polymeric and are usually hydrophobic in nature, with themost common examples including silicones (or polysiloxanes),fluoropolymers, and polyolefins. The slip agent moiety of the presentinvention may be derived from such conventional slip agents and mayinclude, for example, silicones, fluoropolymers, and/or polyolefins incombination with polyesters, polyethers and polycarbonates. Additionalsuitable slip agents are disclosed in, for example, the article entitled“Release Agents” published in the Encyclopedia of Polymer Science, 2ndEd., Vol. 14, Wiley-Interscience, 1988, pgs. 411-421, the completedisclosure of which is hereby incorporated by reference. Although slipagents operate over a wide variety of interfaces, the present inventionis particularly concerned with an interface of a glass surface, and inparticular, the inorganic-organic coating interface between the innerprimary coating and the surface of the optical glass fiber. A typicalslip agent moiety of the composite oligomer is derived from one of theaforementioned slip agents that is covalently incorporated into thecomposite oligomer.

[0112] In a preferred embodiment, the slip agent moiety is the principalcomponent of the oligomer in terms of weight percent because the slipagent moiety itself is usually oligomeric in nature, and the glasscoupling and radiation-curable moieties are usually of lower molecularweight. For example, the slip moiety can be up to about 95 wt. %,relative to the total weight of the composite oligomer, when the threemoieties are directly linked together. However, when an oligomericbackbone is present, the slip agent usually can be up to about 85 wt. %,relative to the total weight of the composite oligomer. As with themolecular weight of the composite oligomer of the present invention, themolecular weight of the slip agent moiety is not strictly limited, butwill generally be between about 150 and about 9,500, preferably, betweenabout 400 and about 4500.

[0113] As with the molecular architecture of the oligomer, there is noparticular limitation on the molecular architecture of the slip agentmoiety, although in general, substantially linear structures can beused. Non-linear or branched structures, however, are not excluded.Oligomeric slip agent moieties, when present, may contain differentkinds of repeat units, although preferably, there is one main type ofrepeat unit.

[0114] Oligomeric silicone slip agent moieties are preferred, andoligomeric silicones comprising substantial portions of methyl sidegroups are particularly preferred. The side groups preferably imparthydrophobic character to the silicone. Other preferred side groupsinclude ethyl, propyl, phenyl, ethoxy, or propoxy. In particular,dimethylsiloxane repeat units represented by the formula, “—OSi(CH₃)₂—”are preferred.

[0115] In a preferred embodiment, the end groups on a substantiallylinear silicone oligomer can be linked with a radiation-curable moietyat one end and a slip agent moiety at the other end. Such linkage caninvolve intermediate linkage groups. Although linkage at the siliconeoligomer end group is preferred, the silicone moiety can be tailored forlinkage with slip agent and radiation-curable moieties at other pointsin the oligomer molecule besides the end groups. For example, functionalgroups can be incorporated throughout the molecular structure of thesilicone oligomer that are linked with the radiation-curable and slipagent moieties. Examples of functionalized silicones which can beincorporated into the oligomer include polyether, polyester, urethane,amino, and hydroxyl.

[0116] Other suitable types of slip agent moieties include those derivedfrom fluorinated slip agents. Examples of such fluorinated slip agentsinclude FC-430, FX-13, and FX-189 (Minnesota Mining and Manufacturing),Fluorolink E (Ausimont), and EM-6 (Elf Atochem).

[0117] Generally, the composite oligomer of the present invention issurface active because of the glass coupling moieties, and inparticular, may tend to concentrate at coating interfaces, such as theinorganic-organic interface, if not bound in the inner primary coating.However, the covalent binding of the composite oligomer after cure, dueto the radiation-curable moiety, may retard such surface activity ormigration. Surface activity means that the composite oligomer, whenplaced in a formulation, tends to migrate to the surface of theformulation rather than be dispersed evenly throughout the formulation.

[0118] The radiation-curable moiety should help ensure that thecomposite oligomer is covalently linked within a radiation-curablecoating so that the composite oligomer cannot be extracted orvolatilized from the cured coating without breaking covalent bonds.

[0119] The radiation-curable moiety can include any functional groupcapable of polymerizing under the influence of, for example, ultravioletor electron-beam radiation. One type of radiation-curable functionalityis, for example, an ethylenic unsaturation, which in general ispolymerized through radical polymerization, but can also be polymerizedthrough cationic polymerization. Examples of suitable ethylenicunsaturation are groups containing acrylate, methacrylate, styrene,vinylether, vinyl ester, N-substituted acrylamide, N-vinyl amide,maleate esters and fumarate esters. Preferably, the ethylenicunsaturation is provided by a group containing acrylate, methacrylate orstyrene functionality. Most preferably, the ethylenic unsaturation isprovided by a group containing acrylate functionality.

[0120] Another type of functionality generally used is provided by, forexample, epoxy groups, or thiol-ene or amine-ene systems. Epoxy groups,in general, can be polymerized through cationic polymerization, whereasthe thiol-ene and amine-ene systems are usually polymerized throughradical polymerization. The epoxy groups can be, for example,homopolymerized. In the thiol-ene and amine-ene systems, for example,polymerization can occur between a group containing allylic unsaturationand a group containing a tertiary amine or thiol.

[0121] The amount or number of glass coupling, slip agent, and radiationcurable moieties in the composite oligomer is not particularly limitedprovided that advantages of the present invention can be achieved andthe inventive concept is practiced. Thus, a single molecule of thecomposite oligomer can contain multiple numbers of glass coupling, slipagent, or radiation-curable moieties, although in a preferredembodiment, a single oligomeric molecule contains one glass coupling,one slip agent, and one radiation-curable moiety.

[0122] The glass coupling, slip agent, and radiation curable moietiesshould be covalently linked together in the oligomer. There is noparticular limitation to how this linkage is effected provided thatadvantages of the present invention are achieved and the inventiveconcept practiced. Linkage may entail direct linkage to the oligomer, oralternatively, indirect linkage to the oligomer. Intermediate linkinggroups will generally operate by way of two functional groups on alinking compound which can link, for example, the radiation-curablemoiety with the slip agent moiety, or link the glass coupling moietywith the slip agent moiety.

[0123] Representative linking compounds include diisocyanate compounds,wherein linkage occurs by formation of urethane, thiourethane, or urealinks by reaction of hydroxyl, thiol, and amino groups respectively,with isocyanate. Such diisocyanate compounds are well-known in thepolyurethane and radiation-curable coating arts. Aromatic or aliphaticdiisocyanates can be used, although aliphatic diisocyanates arepreferred. Other linkages can be through, for example, carbonate, etherand ester groups. Preferably, urethane, urea or thiourethane groups areused as the linking groups.

[0124] The oligomer, therefore, preferably comprises within itsstructure at least one linkage represented by

—NH—CO—X—

[0125] wherein X is an oxygen, sulfur, or nitrogen atom. Urethane andthiourethane groups are most preferred. Urethane groups, for example,can hydrogen bond.

[0126] Although the present invention is not limited to one particularmolecular architecture for the composite oligomer, in a preferredembodiment which makes use of intermediate linking groups, the compositeoligomer can be represented by the following generic structure:

R-L₁-A-L₂C

[0127] wherein

[0128] A represents the slip agent moiety,

[0129] R represents a radiation-curable moiety,

[0130] C represents the glass coupling moiety, and

[0131] L₁ and L₂ represent linking groups.

[0132] L₁ and L₂ can be independently any group capable of providing acovalent link between the “R” moiety and the “A” moiety or between the“C” moiety and the “A” moiety. Based on the disclosure provided herein,one skilled in the art will easily be able to understand what linkinggroups are suitable for the particular “A”, “C” and “R” groups selected.

[0133] In particular, urethane and thiourethane groups are preferred.Urethane and thiourethane linking groups are formed by, for example, (i)linking a hydroxyl end-capped oligomer with a low molecular weightdiisocyanate compound at both oligomer ends without extensive couplingof the oligomer, (ii) linking the isocyanate end-capped oligomer with alow molecular weight hydroxyacrylate compound, or (iii) linking theisocyanate end-capped oligomer with a low molecular weight mercaptocompound.

[0134] The linking groups, however, are considered optional. In otherwords, the oligomer also can be represented by the following genericstructures:

R-L₁-A-C,

R-A-L₂-C,

[0135] or

R-A-C.

[0136] Although the present invention is disclosed in terms of theaforementioned groups or moieties, other groups can in principle beincorporated into the molecular structure to the extent that theadvantages of the present invention can be achieved and the inventiveconcept practiced.

[0137] A preferred embodiment of the present invention is thepreparation of a composite oligomer with use of the followingingredients: a silicone oligomer having two hydroxyl end groups (slipagent moiety), isophorone diisocyanate (linkage), hydroxyethyl acrylate(radiation-curable moiety), and mercaptopropyl silane (glass couplingmoiety). Isophorone diisocyanate (IPDI) serves to end-cap both ends ofthe silicone diol oligomer and provide a linking site with thehydroxyethyl acrylate at one end of the silicone oligomer and with themercaptopropyl silane at the other end.

[0138] A preferred application for the composite oligomer is as anoligomeric additive, or even as a main oligomeric component, in aradiation-curable coating, and in particular, an inner primary, opticalglass fiber coating. The amount of oligomeric additive incorporated intothe radiation curable matrix is not particularly limited but will besufficient or effective to achieve the specific performance objectivesof the particular application. In general, however, a suitable amountwill be between about 0.5 wt. % and about 90 wt. %, preferably, betweenabout 0.5 wt. % and about 60 wt. %, and more preferably, between about0.5 wt. % and about 30 wt. % with respect to the total weight of theradiation-curable coating formulation. In general, higher molecularweight composite oligomers will be present in a radiation-curablecoating in greater weight percentages than lower molecular weightcomposite oligomers.

[0139] The composite oligomer functions to tailor the properties offormulations which exhibit too great a coefficient of friction or toolow adhesion. Specifically, the composite oligomer can increase theadhesion if the adhesion is unacceptably low, and in particularunacceptably low in the presence of moisture. Alternatively, thecomposite oligomer can reduce the coefficient of friction of a coating.Conventional coupling additives and slip agents cannot perform this dualfunction.

[0140] If desired, although a reduction in the number of additives isdesirable, the composite oligomer can be used in conjunction with othercoupling and slip agents to improve absolute performance orcost-performance. In a preferred embodiment, for example, the compositeoligomer can be used in conjunction with a functional organosilanecompound such as, for example, mercaptopropyl silane. For example, ahydroxybutylvinylether adduct with OCN—(CH₂)₃Si(OCH₃)₃ can also be usedtogether with the composite oligomer.

[0141] The composite oligomer can be incorporated into a wide variety ofradiation-curable formulations. There are no particular limitationsprovided that the inventive concept is practiced and advantages accrue.One skilled in the art of formulating radiation-curable coatings willeasily be able to incorporate the composite oligomer therein to providethe desired properties.

[0142] In optical glass fiber coating applications, for example, otherformulation components generally include:

[0143] (i) at least one multi-functional radiation-curable oligomer,which is a different oligomer than the composite oligomer of the presentinvention, to provide a cross-linked coating;

[0144] (ii) at least one reactive diluent to adjust the viscosity to alevel acceptable for application to optical glass fibers, and

[0145] (iii) at least one photoinitiator.

[0146] Additives such as antioxidants, and as already noted, couplingand slip agents may also be utilized.

[0147] Radiation-curing is generally rapidly effected with use ofultraviolet light, although the present invention is not so limited, anda person of skill in the art can determine the best cure method.Radiation-curing results in polymerization of at least some of theradiation-curable moieties present in the composite oligomer whichcovalently links the composite oligomer to itself or, more preferably,other radiation-curable components in the formulation. The chemicalprocesses which occur upon mixing and curing formulations are in somecases complex and may not be fully understood. The present invention,however, is not limited by theory and can be readily understood andpracticed by persons of skill in the art. The formulations of thepresent invention, just like the composite oligomer, can be inpre-cured, partially cured, and in cured states.

[0148] The composite oligomer can be incorporated into inner primarycoating compositions, outer primary coating compositions, inkcompositions and matrix forming compositions. The composite oligomeralso can be incorporated into so-called single coating systems.

[0149] In general, the coating substrate, which includes optical fiber,will be an inorganic or glass substrate, although in principle, othersubstrates such as polymeric substrates may also be effectively used.The glass coupling moiety of the oligomeric additive preferably has thecapacity to couple the substrate. In a preferred application, thecoating substrate is an optical glass fiber, and in particular, afreshly drawn, pristine optical glass fiber. Freshly prepared opticalglass fiber is known in the art to be responsive to glass couplingagents. Exemplary methods of coating optical fibers are disclosed in,for example, U.S. Pat. Nos. 4,474,830 and 4,913,859, the completedisclosures of which are hereby incorporated by reference.

[0150] The present inventions will be further explained by use of thefollowing non-limiting examples.

EXAMPLE 1-1 Comparative Examples 1-A and 1-B

[0151] Synthesis of a Composite Oligomer

[0152] A 1,000 mL four-necked flask was charged with isophoronediisocyanate (55.58 g). 2,6-di-tertbutyl-4-methylphenol (0.12 g) anddibutyltin dilaurate (0.24 g) were added to the flask. 14.51 grams ofHydroxyethyl acrylate was added over a 90 minute period whilemaintaining the temperature below 40 C. At the end of 90 minutes, thetemperature was increased to 40 C., and the mixture was stirred at 40 C.for one hour. The temperature was allowed to decrease to about 30 C.Mercaptopropyl silane (28.13 g of an 87.1% pure product) was added over90 minutes during which time the temperature was maintained below 40 C.After the addition of mercaptopropyl silane, the temperature wasincreased to 40 C., and the reaction mixture was stirred at 40 C. for17-18 hours. 300 g of a 50% ethoxylated polydimethylsiloxane diol of1200 equivalent weight Q4-3667 (Dow Corning) was then added, and thetemperature was increased to 70 C. After about six hours, the isocyanatecontent was measured to be about zero percent. The temperature wasdecreased to 50 C. Based on the reaction conditions and reactants, acomposite silicone silane acrylate oligomer was formed having thefollowing structure:

H-I-(Q4-3667)-I-M

[0153] wherein:

[0154] H=hydroxyethylacrylate,

[0155] I=isophorone diisocyanate,

[0156] Q4-3667=the above described silicone diol, and

[0157] M=mercaptopropyl silane

[0158] Preparation of Radiation-Curable, Optical Fiber Inner PrimaryCoating Compositions

[0159] The components shown in Table 1A were combined, except for thecomposite oligomer and the silane coupling agent. The components wereheated to about 60° C. and mixed to form homogeneous mixtures. Thecomposite oligomer and silicone coupling agent were mixed therein andthe mixture was heated for approximately 15 minutes at 60° C. to form animproved radiation-curable, inner primary, optical glass fiber coatingcomposition, Example 1-1. The mixtures for Comparative Examples 1-A and1-B were prepared similarly. Drawdowns of the compositions were made andthen suitably cured by exposure to UV light to form cured coatings. Thecured coatings were tested for resistance to delamination and fiberpull-out residue and the results are presented in Table 1A. TABLE 1AComp. Ex. Comp. Ex. Component (wt. %) Ex. 1-1 1-A 1-B Urethane acrylateoligomer 53.2 56 53.87 Isodecyl Acrylate 13.3 14 13.47Ethoxylated-nonylphenol 24.22 25.5 24.53 Monoacrylate Composite Oligomer5 0 0 H-I-Q4-3667-I-A189 Q4-3667 (Dow Coming) 0 0 3.8 Photoinitiator2.85 3 2.89 Antioxidant 0.47 0.5 0.48 y-Mercapto-propyl 0.95 1.0 0.96Trimethoxy-Silane Fiber Pull-out Residue Test no residue lots of noresidue residue 60° C. Water Soak none none After 1 hour, DelaminationTest* delamination

[0160] Comparative Example 1-A was a formulation which did not containthe composite oligomer of the present invention, but which contained asilane coupling agent. However, poor results were obtained in thepull-out test because adhesion was too strong. Comparative Example 1-Bwas a formulation which contained a conventional silicone slip agent.The silicone slip agent improved the results of the pull-out testcompared to Comparative Example 1-A, but only at the expense ofhydrolytic interfacial adhesion. Example 1-1 was a formulation thatcontained the composite oligomer of the present invention. The compositeoligomer remarkably improved the results of the pull-out test but not atthe expense of hydrolytic interfacial adhesion.

EXAMPLES 1-2 & 1-3 Comparative Examples 1-C & 1-D

[0161] These Examples and Comparative Examples were conducted todemonstrate the effect of the composite oligomer on glass plateadhesion. The formulations shown in Table 1B were prepared in the samemanner as in Example 1-1 and Comparative Examples 1-A and 1-B. Thesilicone silane acrylate oligomer was prepared in the same manner as inExample 1-1, except that a silicone diol HSi-2111 (Tego Chemie) was usedinstead of Q4-3667 (Dow Corning). TABLE 1B Comp. Ex. 1- Comp. Ex. 1-Component (wt. %) Ex. 1-2 Ex. 1-3 C D Oligomer C 49.22 49.22 49.22 49.22H-I-(PTHF2000-I)₂-H Ethoxylated 24.76 24.76 24.76 24.76 nonylphenolAcrylate Lauryl Acrylate 16.64 16.64 16.64 16.64 2,4,6-trimethylbenzoyl3.0 3.0 3.0 3.0 Diphenyl Phosphine Oxide Thiodiethylene bis(3,5-di- 0.460.46 0.46 0.46 Tert-Butyl-4- Hydroxy)hydrocinnamate gamma-Mercaptopropyl0.92 — 0.92 — Trimethoxy Silane Composite Oligomer 5 5 — —H-I-HSi2111-I-M Adhesion at 50% RH (g/in) 45 14 27 9 Adhesion at 95% RH(g/in) 34 12 20 4 60° C. Water Soak After 24 After 15 After 8 hours,After 15 Delamination Test* hours, no minutes, no minutes, delaminationslight delamination; Delamination delamination After 24 hours slightdelamination

[0162] The results in Table 1B indicate that the composite oligomer isnot only able to improve adhesion to the glass surface, but is also ableto act synergistically with a conventional silane coupling agent.

[0163] 2) Soluble Wax

[0164] Wax can be added as a slip enhancing component to lower the fiberfriction between the inner primary coating and the surface of theoptical fiber but not to the extent that it lowers the adhesion to anunacceptable level. Although numerous waxes are known, many waxes do notdissolve well in inner primary coatings and therefore they tend toseparate out from solution. Furthermore, conventional waxes tend tocause the resulting inner primary coating to be hazy in appearance,which is undesirable. The term “soluble wax” is used herein to designatethose waxes which are sufficiently soluble in the inner primary coatingcomposition at the concentration required to provide the desired levelof fiber friction. The term “wax” is understood to include waxes asdefined in Hawley's “Condensed Chemical Dictionary”, 11th edition, thesaid definition being incorporated herein by reference.

[0165] It has been found that by selecting modified waxes or bymodifying the waxes, the incompatibility problems can be substantiallyavoided. In selecting a modified wax, the solubility of the modified waxin the desired inner primary composition should first be considered.Usually, waxes tend to be insoluble in inner primary coatingcompositions. The solubility of the wax in the inner primary coatingwill depend mainly upon the following: i) the relative polarity of thewax and the polarity of the monomers and oligomers present in the innerprimary composition, ii) the respective types of functional groupspresent in the wax and the monomers and oligomers present in the innerprimary composition, and iii) the similarity between the molecularstructure of the wax and the oligomers or monomers present in the innerprimary composition, such as aliphatic/aromatic, unsaturated/saturated,linear/branched, etc., entities.

[0166] For example, the solubility of the wax can be increased byincorporating functional groups which are similar to those present inthe oligomers or monomers present in the inner primary composition. Ifthe inner primary composition contains monomers or oligomers havingester groups, then ester groups can be incorporated into the molecularbackbone structure of the wax or the ester groups can be grafted ontothe backbone of the wax. Alternatively, wax-like, long-chain fattyesters can be used. Commercial examples of suitable fatty estersinclude:

[0167] Laneto-50 and 100 (PEG-75 lanolin),

[0168] Laneto-AWS (PPG-12-PEG-50 lanolin),

[0169] Ritacetyl (acetylated lanolin),

[0170] Ritahydrox (hydroxylated lanolin),

[0171] Ritasol (isopropyl lanolate),

[0172] Ritalan (lanolin oil),

[0173] Ritalan AWS (PPG-12-PEG-65-lanolin oil),

[0174] Ritawax (lanolin alcohol),

[0175] Supersat (hydrogenated lanolin),

[0176] Forlan C-24 (choleth-24 and Ceteth-24),

[0177] Ritachol 1000 (cetearyl alcohol, polysorbate 60,PEG-150-stearate, and steareth-20),

[0178] Ritapro 100 (cetearyl alcohol, steareth-20, and steareth-10),

[0179] Pationic ISL (sodium isostearoyl lactylate),

[0180] Pationic CSL (calcium stearoyl lactylate),

[0181] Pationic SSL (sodium stearoyl lactylate),

[0182] Pationic SBL (sodium behenoyl lactylate),

[0183] Pationic 138C (sodium lauroyl lactylate),

[0184] Pationic 122A (sodium caproyl lactylate),

[0185] Pationic SCL (sodium cocoyl lactylate),

[0186] Ritox 36 (laureth-23),

[0187] Ritox 52 (PEG-40 stearate),

[0188] Rita CA (cetyl alcohol),

[0189] Rita SA (stearyl alcohol), and

[0190] Rita Cetearyl Alcohol 70/30, (RITA Corp.). Preferably, the fattyester modified wax is isocetyl stearate.

[0191] If the inner primary composition contains monomers or oligomershaving alkoxy or hydroxy groups, then to increase the solubility of thewax, alkoxy or hydroxy groups, including for example ethoxy and propoxygroups, can be incorporated into the molecular backbone structure of thewax or the alkoxy groups can be grafted onto the backbone of the wax.Commercial examples of such modified waxes include the Unilin™ series ofalcohol modified waxes from Petrolite, and Ritawax (lanolin alcohol),

[0192] Ritachol 1000 (cetearyl alcohol, polysorbate 60,PEG-150-stearate, and steareth-20),

[0193] Ritapro 100 (cetearyl alcohol, steareth-20, and steareth-10),

[0194] Rita CA (cetyl alcohol),

[0195] Rita SA (stearyl alcohol), and

[0196] Rita Cetearyl Alcohol 70/30, (RIFA Corp.). Preferably, the alkoxymodified wax is polypropyleneglycol₁₂polyethyleneglycol50lanolin.

[0197] As another example, if the inner primary composition containsmonomers or oligomers having amine groups, then to increase thesolubility of the wax, amine groups can be incorporated into themolecular backbone structure of the wax or the amine groups can begrafted onto the backbone of the wax. An example of such a modified waxis the Armeen™ series of amine modified waxes (Armak), such as Armeen TD(tallowamine),

[0198] Armeen O, OL or OD (oleylamines),

[0199] Armeen SD (soyaamine),

[0200] Armeen 18 (octadecylamine),

[0201] Armeen HT, HTD or 2HT (hydrogenated tallow),

[0202] Armeen T or TM-97 (tallowamine),

[0203] Armeen 12D (dodecylamine),

[0204] Armeen C or CD (cocoamine),

[0205] Armeen 16D (hexadecylamine),

[0206] Armeen 2C (dicocoamine),

[0207] Armeen M2C (methyldicocoamine),

[0208] Armeen DM12D (dimethyldodecylamine),

[0209] Armeen DMCD or DMMCD (dimethylcocoamine),

[0210] Armeen DM14D (dimethyltetradecylamine),

[0211] Armeen DM16D (dimehylhexadecylamine),

[0212] Armeen DM18D (dimethyloctadecylamine),

[0213] Armeen DMHTD (dimethyl(hydrogenatedtallow)amine,

[0214] Armeen DMTD (dimethyltallow amine),

[0215] Armeen DMSD (dimethylsoyamine) or

[0216] Armeen DMOD (dimethyltallow amine). Preferably, the aminesubstituted wax is methyl di(hydrogenated tallow)amine.

[0217] An example of a further functional group that can be incorporatedinto the wax includes carboxylic acids. Suitable examples of saturatedmodified waxes include capric acid, lauric acid, myristic acid, palmiticacid, and stearic acid. Examples of suitable unsaturated waxes includeoleic acid, ricinoleic acid, linoleic acid, and linolenic acid.

[0218] The functional groups present on the modified wax do notnecessarily have to be identical with those present in the oligomers ormonomers of the inner primary coating composition in order to achieveincreased solubility. Functional groups having similar properties, suchas hydrogen bonding, polarity, etc., can be mixed and matched as desiredto increase solubility.

[0219] The solubility of the wax can also be increased by modifying awax or selecting a wax having a similar molecular structure to that ofthe monomers and oligomers present in the inner primary composition. Forexample, if the monomers and oligomers contain aromatic groups, the waxcan be selected or modified to contain aromatic groups. If the monomersor oligomers contain substantial amounts of unsaturation, then the waxcan be modified or selected to contain substantial amounts ofunsaturation. Furthermore, if the monomers or oligomers aresubstantially linear, then a substantially linear wax can be utilized.Commercial examples of substantially linear waxes include Polymekon,Ceramer 67 and 1608, and Petrolite C-400, CA-11, WB-5, WB-11, and WB-17(Petrolite).

[0220] Based on the teachings provided herein, one skilled in the artwill be able to modify or select the desired wax, and to use theselected wax in an amount to provide the desired level of fiber frictionbetween the inner primary coating and the surface of the optical glassfiber. The amount of the wax present in the inner primary compositionwill depend on (1) the ability of the wax to impart the desiredreduction in the fiber friction between the inner primary coating andthe surface of the optical glass fiber, and (2) the solubility of thewax in the inner primary composition. The greater the solubility of thewax in the inner primary composition, the greater the amount of wax thatcan be present. The greater the ability of the wax to reduce fiberfriction, the less wax that will be required. The amount of wax presentshould be about the minimum amount necessary to provide the desiredlevel of fiber friction.

[0221] It has been found that suitable amounts of modified wax includefrom about 0.01% to about 10% by weight of the total inner primarycomposition, more preferably about 0.01% to about 5%, and mostpreferably about 0.01% to about 2%.

[0222] If desired, the wax can be further modified to include aradiation-curable functional group that can copolymerize withradiation-curable monomers and oligomers present in the inner primarycomposition. An example of such a radiation-curable functional wax isstearyl acrylate. The radiation-curable functional group in general doesnot have to be an acrylate group, but can be any known radiation-curablefunctional group, including those described herein.

[0223] The invention will be further explained by the followingnon-limiting examples illustrating the use of waxes.

EXAMPLES 2-1 THROUGH 2-4

[0224] The components shown in Table 2 were combined to form four innerprimary coating compositions. Drawdowns of the inner primary coatingcompositions were made and then cured by exposure to UV light from aFusion D lamp, under a nitrogen atmosphere. The crack propagation andfiber friction for each of the films were tested in the same manner asabove. The results are shown in Table 2. TABLE 2 COMPONENT (wt. %) Ex.2-1 Ex. 2-2 Ex. 2-3 Ex. 2-4 Linear Urethane Acrylate Oligomer 23 — — —Having a Weight Average Molecular Weight of 5000, Urethane AcrylateOligomer — 51.9 42.3 42.3 H-I-PTGL2000-I-PTGL2000-I-H Lauryl Acrylate —16 — — Ethoxylated Nonylphenol Acrylate 64.4 25.6 46.2 46.2 GlycerylPropoxy Triacrylate 8 — — — Phenoxyethyl Acrylate — — 5 52,4,6,-Trimethyl 3 3 3 3 PhenylbenzoylDiphenyl Phosphine OxideThiodiethylene bis .5 0.5 0.5 0.5 (3,5-di-tert-butyl-4-hydroxy)hydrocinnamate Polyethylene/maleic anhydride .1 — — — copolymerwax (ceramer 1608) Methyl di(hydrogenated tallow) — 2 — — Amine IsocetylStearate — — 2 — PPG₁₂PEG₅₀ Lanolin — — — 2 Mercaptopropyl TrimethoxySilane 1 1 1 1 Test results Clarity Clear Clear Clear Clear Viscosity(mPa.s, 25 C.) 7650 6760 7390 Fiber Friction (g/mm) 7.7 11.4 7.2 CrackPropagation (mm) 1.53 1.56 1.69 Fiber Pull-out Residue Test 2.3

[0225] 3) Radiation-Curable, Silicone Containing Oligomers and Use ofNon-Radiation-Curable Silicone Compounds

[0226] Radiation-curable, silicone containing monomers and oligomers canalso be used to adjust the level of fiber friction and thereby improveribbon strippability of the inner primary coating. Theradiation-curable, silicone oligomer comprises a silicone compound towhich at least one radiation-curable functional group is bound.Preferably, two or more radiation-curable functional groups areconnected to the silicone entity.

[0227] Preferably the radiation-curable functional group is capable ofcopolymerizing with the radiation-curable monomers and oligomers presentin the inner primary composition when exposed to suitable radiation.Therefore, the selection of the functional group will depend on themonomer or oligomer present in the inner primary composition. Oneskilled in the art will readily be able to determine which functionalgroups will cross-link with the monomer or oligomer present in the innerprimary composition. While not being limited thereto, examples ofsuitable functional groups are groups containing vinyl, acrylate,methacrylate, maleate, vinyl ether, or acrylamides, as well as thosedescribed herein above.

[0228] Examples of commercially available silicone compounds containinga radiation-curable functional group are silicone acrylates Ebecryl 350and Ebecryl 1360 (Radcure Industries), Tego Rad 2100, 2200, 2500, and2600 (Tego Chemie), and Coat-O-Sil 3503 (OSI Specialties).

[0229] Alternatively, based on the teachings herein, one skilled in theart will be able to modify known silicone compounds to include therequired radiation-curable functionality. For example, a siliconecompound provided with hydroxy functionality can be reacted with adiisocyanate compound and a compound containing a hydroxy and aradiation-curable functionality to provide a radiation-curablefunctionality to said silicone compound. Specific examples includereacting a silicone compound containing a hydroxy functionality with adiisocyanate and hydroxyethylacrylate to provide an acrylatefunctionality on the silicone compound, or isocyanate andhydroxybutylvinylether to provide a vinyl ether functionality on thesilicone compound. Example of suitable silicone compound containinghydroxyl functionality include: polydimethylsiloxane diol of 1200equivalent weight Q4-3667, DC 193 and DC 1248 (Dow Corning), HSi2111(Tego Chemie), and Coat-O-Sil 3500 and 3505 (Osi Specialties).

[0230] Alternatively, non-radiation-curable silicone compounds(hereinafter referred to as “inon-reactive silicone”) can be used toadjust the fiber friction and thereby improve ribbon strippability ofthe inner primary coating.

[0231] U.S. Pat. No. 4,496,210, which is incorporated herein byreference, discloses examples of suitable non-reactive silicones thatcan be used. Non-reactive silicones can be used separately or inconjunction with the radiation-curable silicone oligomers describedherein.

[0232] The radiation-curable silicone oligomer and/or non-reactivesilicone should be present in an amount to provide a fiber friction thatresults in a resistive force that is less than the cohesive strength ofthe inner primary composition. The amount of radiation-curable siliconeoligomer and/or non-reactive silicone is preferably the minimum amountrequired to provide a fiber friction that results in a resistive forceless than the cohesive strength of the inner primary composition. Suchminimum amount can easily be determined by making test runs of innerprimary compositions in which the amount of radiation-curable siliconeoligomers and/or non-reactive silicones present is varied. The lowestamount of radiation-curable silicone oligomers and/or non-reactivesilicones present which provides a fiber friction that results in aresistive force that is less than the cohesive strength of the innerprimary coating is the preferred amount.

[0233] A long chain silicone compound containing on average about oneradiation-curable functional group (monofunctional) bound near aterminus of the silicone compound can provide further advantages. Theend of the long silicone chain furthest from the radiation-curablefunctional group can be mechanically bound in the inner primary coating.However, upon heating during ribbon stripping, it is believed that theend of the long silicone chain farthest from the radiation-curablefunctional group can become unbound and diffuse toward the optical glassfiber/inner primary coating interface which is in the direction the heatis propagating. This diffusion of silicone increases at the criticalmoment during ribbon stripping to facilitate the clean removal of theentire coating system. The silicone acts as a lubricant between thesurface of the optical glass fiber and the inner primary coating.

[0234] The thickness of an inner primary coating usually varies fromabout 10 microns to about 35 microns. Thus, a mono-functionalizedsilicone fluid having a molecular chain length of about 50,000 to about350,000 Daltons can diffuse toward the glass/inner primary coatinginterface during ribbon stripping.

[0235] Suitable amounts of radiation-curable silicone oligomers and/ornon-reactive silicones can also be closely approximated by using thefriction and crack propagation test methods described herein, in whichthe amounts of radiation-curable silicone oligomers and/or non-reactivesilicones that provide a balance between adhesion and ribbon strippingcleanliness of less than about 3 are preferred.

[0236] The amount of radiation-curable silicone oligomer and/ornon-reactive silicones will also depend on the selection of the innerprimary composition, in particular the initial fiber friction of theselected inner primary coating composition. Generally, the higher theinitial fiber friction (no slip additive), the greater the amount ofradiation-curable silicone oligomer and/or non-reactive silicone thatwill be required to lower the fiber friction to a level that provides aresistive force lower than the cohesive strength of the inner primarycoating.

[0237] In general, the radiation-curable silicone oligomers can be usedin greater amounts than non-reactive silicones because it is believedthat the radiation-curable silicone oligomer will become bound in theinner primary coating during curing, whereas the non-reactive siliconeis free to migrate throughout the cured inner primary coating.Alternatively, the radiation-curable silicone oligomer can be the mainoligomer used for forming the inner primary coating. It has been foundthat suitable amounts of radiation-curable silicone oligomer are betweenabout 0.1 to about 90% by weight, preferably about 0.1 to about 60% byweight, and more preferably about 0.1 to about 30% by weight. Ingeneral, higher molecular weight radiation-curable silicone oligomerswill be present in a radiation-curable coating in greater weightpercentages than lower molecular weight composite oligomers.

[0238] Suitable amounts of mono-functionalized monomers have been foundto be about 0.1 to about 20% by weight, more preferably about 0.1 toabout 10% by weight, and most preferably about 0.1 to about 5% byweight.

[0239] Suitable amounts of non-reactive silicone are between about 0.01to about 10% by weight, preferably about 0.01 to about 5% by weight, andmore preferably about 0.01 to about 1% by weight.

[0240] The invention will be further explained by the followingnon-limiting examples illustrating the use of silicone entities.

EXAMPLE 3-1

[0241] The components shown in Table 3A were combined to form an innerprimary coating composition. A film of the coating material (75 micronthick) was prepared on glass slides and then cured by exposure to UVlight in the same manner as above. The tensile strength, elongation andmodulus were measured.

[0242] A 75 micron film of the coating material was also prepared andsuitably cured. The crack propagation was then measured. A friction testwas also conducted, as described herein. The results are shown in Table3A. TABLE 3A Component (wt. %) Example 3-1 OligomerH-DesW-PTHF2900-DesW-H 47.5 Ethoxylated Nonylphenol Acrylate 29 LaurylAcrylate 14.2 2,4,6-Trimethyl Phenylbenzoyl Diphenyl 3 Phosphine OxideSilicone Oligomer 5 H-I-HSi2111-I-H y-Mercaptopropyltrimethoxy Silane .8Thiodiethylene Bis(3,5-di-tert-Butyl-4- .5 Hydoxy)Hydocinnamate TestResults Viscosity, mPa.s (25 C.) 6040 Tensile Strength, Mpa 1Elongation, % 140 Modulus, Mpa 1.4 Dose at 95%, Modulus, J/Sq CM .38Crack Propagation (mm) 1.7 Fiber Pull-Out Friction (g/mm) 17.1

EXAMPLES 3-2 THROUGH 3-10

[0243] The components shown in Table 3B were combined to form 11different inner primary coating compositions. The viscosity and clarityof the compositions was determined.

[0244] Films of the coating materials (75 micron thick) were prepared onmicroscope slides and then cured by exposure to UV light in the samemanner as above. The tensile strength, elongation and modulus weremeasured.

[0245] Additional films of the coating materials were also prepared andsuitably cured. The crack propagation was then measured. A friction testwas also conducted, as described herein. The results are shown in Table3B. TABLE 3B Ex. Ex. Ex. Ex. Ex. Ex. Ex. Ex. Ex. Component (wt. %) 3-23-3 3-4 3-5 3-6 3-7 3-8 3-9 3-10 OligomerH-I-PTHFCD2000-I-PTHFCD2000-I-H 45.67 Oligomer H-(I-PPG1025)1.06-(-ERM)1.14-I-H 54.86 Oligomer H-I-PTGL2000-I-H 60.65 OligomerH-I-PPG2010-I-PPG2010-I-H 67.5 70 Oligomer H-I-PTGL2000-I-PTGL2000-I-H51.0 49.23 43 Oligomer (H-I)₃-TPE4542 78 Ethoxylated NonylphenolAcrylate Ester 34.48 24.99 32.85 20.14 24.75 16 50.5 Lauryl Acrylate14.35 13.72 6.92 16.64 Phenoxyethyl Acrylate 16.62 2.5 Mole PropoxylatedNonyl Phenol Acrylate 25.00 23.5 25:75 weight/weight of Bis(2,6- 2.94 3Dimethoxybenzoyl)(2,4,4-Trimethylpentyl) Phosphine Oxide and2-Hydroxy-2-Methyl-1- Phenyl Propanone 2,4,6-trimethylbenzoyl DiphenylPhosphine 3 2.5 3 3 1 3 Oxide 1-Hydroxycyclohexyl Phenyl Ketone 4 2Octadecyl 3,5-Bis(1,1-Dimethylethyl)-4- .5 .5 HyroxybenzenepropanoneThiodiethylene bis(3,5-di-Tert-Butyl-4- .49 .5 .3 .5Hydroxy)hydrocinnamate Ditridecylthiodipropionate 1 1 Free Silicone,DC-193 (Dow Corning) 1 2 1 2 2 Free Silicone, DC-190 (Dow Corning) 1Teograd 2100 silicone acrylate 2.5 1 5 L-77 Polyethylene oxide modifiedDimethylsiloxane 1-Propanethiol,3-(Trimethoxysilyl) 1 1 .98 1 1 1 .92 11 Clarity When Made clear clear clear clear clear Clarity After 24 Hoursat 4 C clear clear clear Clarity After 24 Hours at −20 C clear clearclear Clarity After 3 Days at 60 C clear clear clear Viscosity (mPa · s,25 C) 8700 5600 8000 9520 7170 6240 8200 Dose @ 95% Modulus (J/sq · cm).77 .46 .45 .32 .36 .45 .2 Tensile Strength (MPa) .4 1.5 .6 1.1Elongation (%) 50 100 140 180 Modulus (Mpa) 1.2 2.7 1.1 1.3 2.4 FiberFriction (g/mm) 3.1 4.9 2.7 4.4 21 18.4 18.5 3 3.4 Fiber Friction (g/mm)After 7 days, 60 C, dose 1 1.4 95% of dose required for complete cureCrack Propagation (mm) 2.1 1.49 1 1.4 1.21 1.82 1.47 1.1 1.9 Crackpropagation (mm) after 7 days, 60 C, dose 1.1 95 of dose required forcomplete cure

[0246] 4) Radiation-curable Fluorinated Oligomers and FluorinatedMaterials

[0247] The fiber friction between the inner primary coating and thesurface of the optical glass fiber can also be significantly reduced byincorporating radiation-curable fluorinated oligomers, monomers and/ornon-radiation curable fluorinated materials into the inner primarycoating composition. The radiation-curable, fluorinated oligomer ormonomer comprises a fluorinated compound to which at least oneradiation-curable functional group is bound. Preferably, two or moreradiation-curable functional groups are connected to the fluorinatedentity.

[0248] Preferably the radiation-curable functional group is capable ofcopolymerizing with the radiation-curable monomers and oligomers presentin the inner primary composition when exposed to suitable radiation.Therefore, the selection of the functional group will depend on themonomer or oligomer present in the inner primary composition. Oneskilled in the art will easily be able to determine which functionalgroups will cross-ink with the monomer or oligomer present in the innerprimary composition. While not being limited thereto, examples ofsuitable radiation-curable functional groups are groups containingvinyl, acrylate, methacrylate, maleate, vinyl ether, or acrylamides, aswell as those described herein above.

[0249] Examples of commercially available fluorinated compoundscontaining at least one radiation-curable functional group includeperfluoro ethyl acrylate (DuPont), 2-(N-Ethylperfluoro OctaneSulfonamido)Ethyl Acrylate (3M), 1H,1H-pentadecafluoroctyl acrylate(Oakwood Research Chemicals), as well as methacrylate or N butylacrylate versions of these.

[0250] Based on the teachings herein, one skilled in the art will beable to modify a fluorinated compound to include the requiredradiation-curable functionality. For example, a fluorinated compoundprovided with hydroxy functionality can be reacted with a diisocyanatecompound and a compound containing a hydroxy and a radiation-curablefunctionality to provide a radiation-curable functionality to saidfluorinated compound. Specific examples include reacting a fluorinatedcompound containing a hydroxy functionality with a diisocyanate andhydroxyethylacrylate to provide an acrylate functionality on thefluorinated compound, or isocyanate and hydroxybutylvinylether toprovide a vinyl ether functionality on the fluorinated compound.Examples of suitable fluorinated compounds containing hydroxylfunctionality include Fluorolink E (Ausimont),2-methyl-4,4,4-trifluorobutanol, 1H,1H-pentadecafluoro-1-octanol,1H,1H-pentafluoropropanol-1, and1H,1H,12H,12H-perfluoro-1,12-dodecanediol (Oakwood Research Chemicals).

[0251] Alternatively, non-radiation-curable fluorinated compounds(hereinafter referred to simply as “fluorinated compounds”) can be usedto adjust the fiber friction and thereby improve ribbon strippability ofthe inner primary.

[0252] The fluorinated compounds can be used separately or inconjunction with the radiation-curable silicone oligomers or monomersdescribed herein.

[0253] The radiation-curable fluorinated oligomer or monomer and/orfluorinated compounds should be present in an amount to provide a fiberfriction that results in a resistive force that is less than thecohesive strength of the inner primary composition. The amount ofradiation-curable fluorinated oligomer and/or fluorinated compound ispreferably the minimum amount required to provide a fiber friction thatresults in a resistive force less than the cohesive strength of theinner primary composition. Such minimum amount can easily be determinedby making test runs of inner primary compositions in which the amount ofradiation-curable fluorinated oligomers or monomers and/or fluorinatedpresent is varied. The lowest amount of radiation-curable fluorinatedoligomers or monomers and/or fluorinated compounds present whichprovides a fiber friction that results in a resistive force less thanthe cohesive strength of the inner primary coating is the preferredamount.

[0254] Suitable amounts of radiation-curable fluorinated oligomers ormonomers and/or fluorinated compounds can also be closely approximatedby using the friction and crack propagation test methods describedherein.

[0255] The amount of radiation-curable fluorinated oligomer or monomersand/or fluorinated compounds will also depend on the selection of theinner primary composition, in particular the initial fiber friction ofthe selected inner primary coating composition. Generally, the higherthe initial fiber friction (no slip additive), the greater the amount ofradiation-curable fluorinated oligomer or monomer and/or fluorinatedcompounds that will be required to lower the fiber friction to a levelthat provides a resistive force lower than the cohesive strength of theinner primary coating.

[0256] In general, the radiation-curable fluorinated oligomers ormonomers can be used in greater amounts than non-reactive fluorinatedcompounds because it is believed that the radiation-curable fluorinatedoligomers or monomers will become bound in the inner primary coatingduring curing, whereas the non-reactive fluorinated compounds are freeto migrate throughout the cured inner primary coating. Alternatively,the radiation-curable fluorinated oligomer or monomer can be the mainoligomer used for forming the inner primary coating. It has been foundthat suitable amounts of radiation-curable fluorinated oligomer ormonomer are between about 0.1 to about 90% by weight, preferably about0.1 to about 60% by weight, and more preferably about 0.1 to about 30%by weight. In general, larger molecular weight oligomers can be used ingreater amounts than lower molecular weight oligomers or monomers.

[0257] Suitable amounts of fluorinated compounds have been found to bebetween about 0.01 to about 10% by weight, preferably about 0.01 toabout 5% by weight, and more preferably about 0.01 to about 1% byweight.

[0258] The invention will be further explained by the followingnon-limiting examples illustrating the use of fluorinated materials.

EXAMPLES 4-1 THROUGH 4-3

[0259] The components shown in Table 4 were combined to form differentinner primary coating compositions. The tests results for thesecompositions are also set forth in Table 4. TABLE 4 Component (wt. %)Ex. 4-1 Ex. 4-2 Ex. 4-3 Oligomer 54.32 55.58H-(I-PPG1025)_(1.06-)(-PERM)_(1.14)-I-H Oligomer H-(I-PPG2010)₂-I-H67.75 Ethoxylated Nonylphenol Acrylate Ester 24.74 25.31 IsodecylAcrylate 13.58 13.9 2.5 Mole Propoxylated Nonyl Phenol Acrylate 25 25:75weight/weight of Bis(2,6- 2.91 3Dimethoxybenzoyl)(2,4,4-Trimethylpentyl) Phosphine Oxide and2-Hydroxy-2-Methyl-1-Phenyl Propanone 1-Hydroxycyclohexyl Phenyl Ketone4 Octadecyl 3,5-Bis(1,1-Dimethylethyl)-4- 0.50 HyroxybenzenepropanoneThiodiethylene bis(3,5-di-tert-butyl-4- .48 .5 hydroxy)HydrocinnamateDitridecylthiodipropionate 1.00 Foralkyl EM-6 TridecafluorooctylMecaptan (Elf 3.00 Autochem) Fluorosulfonamide (3M) 0.75 .75mercaptopropyl trimethoxy silane 0.97 1 1 Clarity as made Clear ClearClear Clarity after 24 hours at 4° C. Clear Clarity after 24 hours at−20° C. Clear Clarity after 3 days at 60° C. Very Few Incompat'sViscosity (mPa.s, 25 C.) 6200 Dose @ 95% Modulus (J/sq.cm) .77 0.50 .47Tensile Strength (MPa) 0.50 Elongation (%) 88 Modulus (MPa) 1.20 FiberFriction (g/mm) 25.5 8.2 10.5 Fiber Friction (g/mm) After 7 days, 60 C.,at dose of 1.1 95% of dose for complete cure Crack Propagation (mm) 1.321.54 1.1 Crack Propagation (mm) after 7 days, 60 C., at dose of 1 95% ofdose for complete cure

[0260] 5) Solid Lubricants

[0261] Solid lubricants can be added to the inner primary composition toreduce the fiber friction between the inner primary coating and thesurface of the optical glass fiber. The term “solid lubricant” is usedherein to mean that the lubricant is substantially insoluble in theinner primary composition and that the particle or flake shape of thesolid lubricant is substantially maintained after curing of the innerprimary coating composition.

[0262] Usually the solid lubricant is non-reactive with the componentsof inner primary coating composition. Examples of suitable non-reactivesolid lubricants include solid organic lubricants including organicpolysaccarides such as sodium alginate, polyolefins, polyvinyl alcohol,nylon such as Orgasol (Elf Atochem), solid Teflon particles, and hardwaxes such as Rad Wax; solid inorganic lubricants including molybdenumdisulfide, graphite, silicates such as talc, clays such as kaolin andmica, silica, and boron nitride.

[0263] However, if desired, a reactive solid lubricant can be used.Reactive solid lubricants contain a radiation-curable functional group.Preferably, the radiation-curable functional group is capable ofcopolymerizing with the radiation-curable monomers or oligomers presentin the inner primary composition. The radiation-curable functional groupcan be, for example, any of the radiation-curable functional groupsdescribed herein. Specific examples of suitable reactive solidlubricants include zinc acrylate, molybdenum acrylate, aluminumacrylate, barium acrylate, and chromium acrylate.

[0264] The particle size is preferably small enough to avoidmicrobending caused by the solid particles exerting stresses on thesurface of the optical glass fiber during use. Furthermore, the particlesize is preferably small enough to avoid causing the inner primarycoating to be hazy in appearance. Examples of suitable particle sizeshave been found to be about 10 microns or less, preferably about 5microns or less, and most preferably less than about 2 microns.

[0265] Alternatively to the particle size, the hardness of the solidlubricant is preferably low enough to avoid microbending caused by thesolid particles exerting stresses on the surface of the optical glassfiber during use. In general, a softer solid lubricant will be lesslikely to cause such microbending.

[0266] Based on the teachings provided herein, one skilled in the artwill easily be able to select a solid lubricant in an amount to providethe desired level of fiber friction between the inner primary coatingand the surface of the optical glass fiber. The amount of the solidlubricant present in the inner primary composition will depend on theability of the solid lubricant to impart the desired reduction in thefiber friction between the inner primary coating and the surface of theoptical glass fiber, and the amount the fiber friction must be reducedto provide a fiber friction level that still maintains sufficientadhesion. In general, the greater the ability of the solid lubricant toreduce fiber friction, the less solid lubricant that will be required.Preferably, the amount of solid lubricant present is about the minimumamount necessary to provide a level of fiber friction necessary toprovide a clean, residue free optical glass fiber after ribbonstripping. As discussed above, the fiber friction level that willprovide a clean, optical glass fiber after ribbon stripping will dependon the cohesive strength of the inner primary coating.

[0267] It has been found that suitable amounts of solid lubricantinclude from about 0.1% to about 20% by weight of the total innerprimary composition, more preferably about 0.1% to about 10%, and mostpreferably about 0.1% to about 5%.

[0268] Preferably, a surfactant is used in combination with the solidlubricant. Examples of a suitable surfactants include: fluorosulfonamidesurfactant (3M), 3,6-dimethyl4-octyne-3,6-diol (Air Products), linearcopolymer of vinylpyrolidone and long chain alpha olefin (InternationalSpecialty Products), Solsperse high MW polymeric dispersing agents(Zeneca), and other well-known anionic, cationic and non-ionicsurfactants.

[0269] The invention will be further explained by the followingnon-limiting examples.

EXAMPLES 5-1 THROUGH 5-3

[0270] The components shown in Table 5 were combined to form differentinner primary coating compositions. The tests results for thesecompositions are also set forth in Table 5. TABLE 5 Component (wt. %)Ex. 5-1 Ex. 5-2 Ex. 5-3 Oligomer H-(I-PTGL2000)₂-I-H 36.1 42.3 36.1Ethoxylated Nonylphenol Acrylate 44.4 46.1 43.9 Phenoxyethyl Acrylate 55 5 2,4,6-trimethylbenzoyl Diphenyl Phosphine 3 3 3 Oxide and2-Hydoxy-2-Methyl-1-Phenyl-1- Propanone blend Thioethylenebis(3,5-di-tert-butyl-4- .5 .5 .5 Hydroxy)Hydrocinnamatey-Mercaptopropyltrimethoxy Silane 1 1 1 Rad Wax 62EB (33% PB wax inepoxy 10 acrylate) Fluorosulfonamide Surfactant FC-430 (3M) .1 .5 FluoroA (Micronized PTFE) 2 10 Test results Clarity yes yes yes Color whitewhite white Viscosity, mPa.s at 25° 5440 7960 7520 Film Opacity, 3 milopaque cloudy cloudy Fiber Friction (g/mm) 15.2 8.2 6.6 CrackPropagation (mm) 1.96 2.2

[0271] 6) Linear Oligomers

[0272] The ability of a ribbon assembly to strip cleanly during ribbonstripping can be further improved if the inner primary coatingcompositions comprises at least one linear, radiation-curable oligomer.Examples of linear, radiation-curable oligomers according to the presentinvention that provide enhanced strippability include those representedby the following formula:

R¹-L-[R²-L]_(n)-R³

[0273] wherein:

[0274] R¹-R³ independently represent an organic group havingradiation-curable functional groups as defined herein, preferably R²represents a substantially linear carbon-containing entity;

[0275] each L independently represents a linking group, providing abridging group such as a urethane, thio-urethane, urea or estergrouping, as defined herein, preferably urethane; and

[0276] n represents a value from 0 to about 40, preferably about 1 toabout 20, and most preferably about 1 to about 10, wherein the molecularweight of [R²-L]_(n) is about 500 to about 20,000, preferably about1,000 to about 10,000, and most preferably about 1,500 to about 6,000.

[0277] When n is 1, [R²-L] may represent, for example, a polyolefin,polyether, polycarbonate, or polyester structure having a molecularweight of about 500 to about 20,000. When n is from about 2 to about 5,[R²-L] may represent, for example, a polyolefin, polyether,polycarbonate, or polyester having a molecular weight of about 500 toabout 10,000. When n is from about 5 to about 30, [R²-L] may represent,for example, a polyolefin, polyether, polycarbonate, or polyester havinga molecular weight of about 500 to about 4,000.

[0278] The linear oligomers according to this invention can be used inan amount suitable to provide the desired level of ribbon strippingperformance. The desired amount can easily be found and determined byone skilled in the art by testing different amounts of the selectedlinear oligomer(s) in an inner primary coating, and optionally in anouter primary coating as well, on optical glass fibers encased in aribbon assembly. It has generally been found that the linear oligomersaccording to this invention can be used in amounts of about 0.1 to about90 wt. %, preferably about 5 to about 80 wt. %, more preferably about 5to about 60 wt. %, based on the total weight of the inner primary orouter primary composition.

EXAMPLE 6-1 THROUGH 6-2

[0279] The components shown in Table 6 were combined to form innerprimary coating compositions. The compositions were cured and the fiberpull-out friction of the cured coating was measured, as defined herein.The test results are shown in Table 6. TABLE 6 Component (wt. %) Example6-1 Example 6-2 Oligomer H-(I-PTHF2000)₂-I-H 52.26 52.26 EthoxylatedNonylphenol Acrylate 15.7 15.67 Lauryl Acrylate 15.19 16.19 n-VinylFormamide Isobornyl Acrylate 11.8 0 n-Vinyl Formamide EthylhexylAcrylate 0 10.8 25:75 weight/weight of Bis(2,6- 3.7 3.7Dimethoxybenzoyl)(2,4,4-Trimethylpentyl) Phosphine Oxide and2-Hydroxy-2-Methyl- 1-Phenyl Propanone gamma-Mercaptopropyl TrimethyoxySilane 0.92 0.92 Thioethylene Bis(3,5 di-tert-butyl-4- .46 .46hydroxyl)Hydrocinnamate (antioxidant)

[0280] 7) Terminal Linear Moieties

[0281] It has been found that the use of radiation-curable oligomerscontaining at least one terminal linear moiety can also improve theefficiency of the inner primary coating to assist in providing a betterstripping of a ribbon assembly.

[0282] Examples of radiation-curable oligomers according to the presentinvention that provide enhanced strippability include those representedby the following formula:

R⁴—x-L-x—[R⁵—x-L-x]_(n)—R⁶

[0283] wherein

[0284] R⁴ represents a substantially linear long chain alkyl terminatingin at least one hydroxyl group;

[0285] each L independently represents a molecular bridging group,preferably derived from a diisocyanate precursor reactant;

[0286] each x independently represents a resulting reacted linkinggroup, such as, inter alia, a urethane, thio-urethane, or urea entity,alternatively, ester linkages can also be utilized;

[0287] R⁵ represents a linear or branched or cyclic hydrocarbon orpolyether moiety derived from a diol and having a molecular weight offrom 150 to 10,000, preferably from 500 to 5,000, and most preferablyfrom 1,000 to 2,000 Daltons;

[0288] R⁶ represents an end group carrying a radiation-curablefunctional group as defined herein, preferably an acrylate ormethacrylate, and also having an hydroxyl linkage to the L entity.

[0289] R⁴ preferably has at least about 80%, more preferably at leastabout 90%, of its carbon atoms in a straight chain; and, n may representa number from zero to 30. Preferably, R⁴ represents about a C₉-C₂₀ alkylradical. Longer carbon chains may decrease the resistance against oil.Suitable examples of alkyls are lauryl, decyl, isodecyl, tridecyl, andstearyl. Most preferred is lauryl.

[0290] R⁵ represents C₆-C₁₅ branched or cyclic aliphatic group havingabout 6 to about 15 carbon atoms. In particular, R⁵ may represent analiphatic component of a diisocyanate compound such as isophoronediisocyanate, DesW, TMDI, and HXDI. If R⁵ is a branched component,preferably, the extent of branching units is at least about 10 mole %,and more preferably at least about 20 mole %, based on the total numberof carbon atoms in R⁵.

[0291] The oligomers according to above formula can be made, forexample, by reacting in a first reaction one mole of a diisocyanatecompound (for forming R⁵) with (1) one mole of a long chain alkylcontaining a hydroxy group (for forming R⁴) or (2) one mole of acompound containing a hydroxy functional group and a radiation-curablefunctional group (for forming R⁶). The urethane linking group “x”attached to “L” is formed by the reaction of the isocyanate group with ahydroxyl group. In a second reaction, the remaining isocyanate group isreacted with the other as yet un-reacted hydroxyl group of the compound.Reactions of hydroxy functional compounds with isocyanate functionalmolecules are well known in the art, and can be catalyzed if needed,with known catalysts. Suitable examples of reactants containing aradiation-curable functional group and a hydroxy group arehydroxyethylacrylate or 2-hydroxypropylacrylate. Suitable examples oflinear long chain alkyls include lauryl alcohol, decyl alcohol, isodecylalcohol, tridecyl alcohol, and stearyl alcohol.

[0292] The resulting radiation-curable oligomer can be used in opticalfiber coating compositions, in particular in inner primary coatings, asa monomer that enhances the strippability of a ribbon assemblycomprising at least one optical fiber coated with a compositions havingsuch an oligomer. In addition, compositions comprising at least one ofthese oligomers may also experience a faster cure speed.

[0293] It has been found that when at least one terminal linear oligomeris present in amounts of about 1 to about 90 wt. %, preferably about 5to about 80 wt. %, and most preferably about 5 to about 60 based on thetotal weight of the inner primary or outer primary composition.

[0294] 8) Aromatic Groups

[0295] Ribbon strippability can also be enhanced by incorporating a highconcentration of aromatic groups in the oligomers and monomers used toform the inner primary coating. It will be appreciated that coatingcompositions comprising about 0.1 or more moles of aromatic groups per100 grams of total composition, calculated using the molecular weightsof the compositional components, are regarded as having a highconcentration of aromatic groups. It is believed that the planarity ofthe phenyl ring next to the surface of the optical glass fiber may allowfor the good slidability of the inner primary coating off the opticalglass fiber during ribbon stripping.

EXAMPLE 8-1

[0296] The components shown in Table 8 were combined to form differentinner primary coating compositions. The tests results for thesecompositions are also set forth in Table 8. TABLE 8 Component Example(Amount is % by weight of total composition) 8-1 OligomerH-I-(PTGL2000-I)₂-H 51.54 Ethoxylated Nonylphenol Acrylate 20.86Phenoxyethyl Acrylate 16.8 Lauryl Acrylate 7 25:75 weight/weight ofBis(2,6- 2.5 Dimethoxybenzoyl)(2,4,4-Trimethylpentyl) Phosphine Oxideand 2-Hydroxy-2-Methyl-1- Phenyl Propanone ThiodiethyleneBis(3,5-di-tert-butyl-gamma- 0.3 hydroxy) Hydrocinnamategamma-Mercaptopropyl Trimethoxy Silane 1 Test Results Crack Propagation(mm) 1.49 Fiber Pull-Out Friction (g/mm) 10

[0297] 9) High Molecular Weight Polymeric Blocks and ReducedConcentration of Urethane

[0298] Radiation-curable, inner primary optical glass fiber coatingcompositions (hereinafter referred to as “inner primary compositions”)are now well known in the art. Such inner primary compositions usuallycontain at least one radiation-curable oligomer, and optionally reactivediluents, photoinitiators, and additives, as described herein above.

[0299] It has now been found that by reformulating the radiation-curableoligomer used in the inner primary composition, an inner primary coatingcan be formed having a significantly increased crack propagation incombination with a significantly decreased fiber friction. Furthermore,it has been found that the crack propagation can be increased and thefiber friction decreased to levels which provide the inner primarycoating with the ability to strip cleanly from the surface of an opticalglass fiber during ribbon stripping, without the use of substantialamounts of slip agents in the inner primary coating. In some instances,the use of slip agents can be substantially avoided. The term slipagents includes components which are separate and distinct from theradiation-curable oligomer as well as slip agent moieties that can bebound to the radiation-curable oligomer. The use of slip agents maycause undesirable delamination of the inner primary coating during useof the ribbon assembly in hot and wet environments, such as tropicalenvironments, which can lead to microbending and attenuation of thesignal transmission. Thus, by substantially avoiding the use of slipagents to provide a ribbon-strippable inner primary coating, the presentinvention can provide a ribbon-strippable inner primary coating whichexhibits enhanced resistance to such undesirable delamination.

[0300] Radiation-curable, oligomers comprising a carbon containingbackbone to which at least one radiation-curable functional group isbound are well known in the art. Usually, the carbon containing backboneof the radiation-curable oligomer contains one or more polymeric blockseach having a molecular weight up to about 2000 and being connectedtogether via coupling groups. Thus, an oligomer having a molecularweight of about 6000, will usually contain three polymeric blocks eachhaving a molecular weight of about 2000 which are connected via couplinggroups. The radiation-curable functional groups are also usuallyconnected to the carbon-containing backbone via coupling groups.

[0301] By extensive experimentation, it has now been found that as themolecular weight of the polymeric blocks is increased, the crackpropagation of the inner primary coating increases and the fiberfriction of the inner primary coating decreases. The molecular weight ofthe polymeric blocks should be adjusted up to level which provides aninner primary coating having a fiber friction and crack propagation thatare suitable for ribbon stripping. Alternatively, the molecular weightof the polymeric block can be adjusted upward to level which provides aninner primary coating having a fiber friction of about 30 g/mm or lessat a rate of 0.1 mm/sec in combination with a crack propagation of atleast about 1.3 mm at a rate of 0.1 mm/sec, at a ribbon strippingtemperature. Preferably, the fiber friction is about 25 g/mm or less andmore preferably about 20 g/mm or less. Preferably, the crack propagationis at least about 1.5 mm and more preferably at least about 2 mm. Thecrack propagation is usually below about 4, but can be higher.

[0302] It has been found that by using polymeric blocks having amolecular weight greater than 2000, preferably at least about 2500, andmost preferably at least about 3000, inner primary coatings having afiber friction and a crack propagation as described above can beprovided. The molecular weight of said polymeric block is usually lessthan about 10,000, preferably less than about 8,000.

[0303] The coupling groups can be any group capable of providing a linkbetween polymer blocks and/or between radiation-curable functionalgroups and polymer blocks. Examples of suitable coupling groups areurethane, urea and thiourethane. For purposes of practicing the presentinvention, which relates to adjusting the crack propagation and fiberfriction using the molecular weight of the polymeric blocks and/orurethane concentration, the following groups are not considered couplinggroups when determining the molecular weight of the polymeric blocks:carbonate, ether, and ester groups. Thus, when determining the molecularweight of the polymeric block, ether groups, carbonate groups, and estergroups are considered part of the polymeric block. Polymeric compoundsseparated by urethane, thiourethane and urea groups are consideredseparate polymeric blocks. Urethane is the preferred coupling group.

[0304] Usually, urethane groups are used as the coupling groups in theradiation-curable oligomer. For example, if an oligomer having a numberaverage molecular weight about 6000 comprising 3 polymer blocks, eachhaving a number average molecular weight of about 2000, and containing 2radiation-curable functional groups, will have four urethane linkages.Two of the urethane linkages connect the radiation-curable groups to thepolymeric blocks and two of the urethane linkages connect the threepolymeric blocks together.

[0305] It has now been found that as the concentration of urethanelinkages present in the inner primary composition is decreased, thecrack propagation of the inner primary coating increases and the fiberfriction of the inner primary coating decreases. Thus, the term urethaneconcentration represents the weight percentage of all urethane linkagespresent in the inner primary coating composition, based on the totalweight of the inner primary coating composition.

[0306] Based on this discovery, the urethane concentration should beadjusted downward to a level which provides an inner primary coatinghaving a fiber friction and crack propagation that are suitable forribbon stripping the desired ribbon assembly. It has been found that ifthe calculated concentration of urethane linkages is about 3.5% byweight or less, relative to the total weight of the composition, innerprimary coatings in conjunction with a relatively high modulus outerprimary coating provide good ribbon strippability. Preferably, theurethane concentration is about 3.0% by weight or less, more preferablyabout 2.5% or less by weight, and most preferably about 2% or less byweight. The urethane concentration effect on fiber friction and crackpropagation is more pronounced for higher molecular weight oligomers,such as about 3,000 to about 10,000, more preferably about 3,500 toabout 8,000. Thus, preferably the urethane oligomer has a molecularweight of about 3,000 to about 10,000 in combination with a urethaneconcentration of about 3.5% by weight or less, more preferably, amolecular of about 3,500 to about 8,000 in combination with a urethaneconcentration of about 3.5% or less, and most preferably, a molecularweight of about 3,500 to about 8,000 in combination with a urethaneconcentration of about 3% or less.

[0307] The polymeric blocks can comprise for example polyethers,polyolefins, polycarbonates, polyesters, polyamides or copolymersthereof. Preferably, the polymeric blocks comprise polyethers.

[0308] The radiation-curable functional groups used can be anyfunctional group capable of polymerization when exposed to actinicradiation. Suitable radiation-curable functional groups are now wellknown and within the skill of the art.

[0309] Commonly, the radiation-curable functionality used is ethylenicunsaturation, which can be polymerized through radical polymerization orcationic polymerization. Specific examples of suitable ethylenicunsaturation are groups containing acrylate, methacrylate, styrene,vinylether, vinyl ester, N-substituted acrylamide, N-vinyl amide,maleate esters, and fumarate esters. Preferably, the ethylenicunsaturation is provided by a group containing acrylate, methacrylate,or styrene functionality, and most preferably acrylate or methacrylate.

[0310] Another type of radiation-curable functionality generally used isprovided by, for example, epoxy groups, or thiol-ene or amine-enesystems. Epoxy groups can be polymerized through cationicpolymerization, whereas the thiol-ene and amine-ene systems are usuallypolymerized through radical polymerization. The epoxy groups can be, forexample, homopolymerized. In the thiol-ene and amine-ene systems, forexample, polymerization can occur between a group containing allylicunsaturation and a group containing a tertiary amine or thiol.

[0311] The radiation-curable oligomer can be easily formed by reacting apolymeric polyol, a compound containing a radiation-curable functionalgroup and a hydroxyl group, and a polyisocyanate. The general reactionof isocyanate functional groups with hydroxyl groups to form urethanelinkages is well known in the art. Thus, one skilled in the art will beable to make the improved oligomer according to the present inventionbased on the disclosure provided herein.

[0312] Examples of suitable polymeric polyols that can be used to formthe radiation-curable oligomer include polyether diols, polyolefindiols, polyester diols, polycarbonate diols, and mixtures thereof.Polyether and polycarbonate diols, or combinations thereof, arepreferred. The polymeric block is the residue of the polymeric polyolafter reaction to form the radiation-curable oligomer.

[0313] If a polyether diol is used, preferably the polyether is asubstantially non-crystalline polyether. Preferably, the polyethercomprises repeating units of one or more of the following monomergroups:

[0314] Thus, suitable polyethers can be made from epoxy-ethane,epoxy-propane, tetrahydrofuran, methyl-substituted tetrahydrofuran,epoxybutane, and the like. Commercial examples of a suitable polyetherpolyols that can be used are PTGL2500, PTGL3000, PTGL3500, and PTGL4000(Hodogaya Chemical Company).

[0315] If a polyolefin diol is used, the polyolefin is preferably alinear or branched hydrocarbon containing a plurality of hydroxyl endgroups. The hydrocarbon provides a hydrocarbon backbone for theoligomer. Preferably, the hydrocarbon is a non-aromatic compoundcontaining a majority of methylene groups (—CH₂—) and which can containinternal unsaturation and/or pendent unsaturation. Examples of suitablehydrocarbon diols include, for example: hydroxyl-terminated;

[0316] fully or partially hydrogenated 1,2-polybutadiene; copolymers of1,4-polybutadiene;

[0317] copolymers of 1,2-polybutadiene;

[0318] polyisobutylene polyol;

[0319] mixtures thereof, and the like. Preferably, the hydrocarbon diolis a substantially, fully hydrogenated 1,2-polybutadiene-ethenecopolymer or 1,2-polybutadiene-ethene copolymer.

[0320] Examples of polycarbonate diols are those conventionally producedby the alcoholysis of diethylene carbonate with a diol.

[0321] Examples of polyester diols include the reaction products ofsaturated polycarboxylic acids, or their anhydrides, and diols.Commercial examples are the polycaprolactones, commercially availablefrom Union Carbide under the trade designation Tone Polylol series ofproducts, for example, Tone 0200, 0221, 0301, 0310, 2201, and 2221. TonePolyol 0301 and 0310 are trifunctional.

[0322] Any organic polyisocyanate, alone or in admixture, can be used asthe polyisocyanate. Examples of suitable diisocyanates include:isophorone diisocyanate (IPDI);

[0323] toluene diisocyanate (TDI);

[0324] diphenylmethylene diisocyanate;

[0325] hexamethylene diisocyanate;

[0326] cyclohexylene diisocyanate;

[0327] methylene dicyclohexane diisocyanate;

[0328] 2,2,4-trimethyl hexamethylene diisocyanate;

[0329] m-phenylene diisocyanate;

[0330] 4-chloro-1,3-phenylene diisocyanate;

[0331] 4,4′-biphenylene diisocyanate;

[0332] 1,5-naphthylene diisocyanate;

[0333] 1,4-tetramethylene diisocyanate;

[0334] 1,6-hexamethylene diisocyanate;

[0335] 1,10-decamethylene diisocyanate; 1,4-cyclohexylene diisocyanate;and polyalkyloxide and polyester glycol diisocyanates such aspolytetramethylene ether glycol terminated with TDI and polyethyleneadipate terminated with TDI, respectively. Preferably, the isocyanatesare TDI or IPDI.

[0336] If other oligomers, monomers, and/or additives containingurethane linkages are used in admixture with the above describedradiation-curable oligomer to form an inner primary composition, theconcentration of urethane linkages present in each other oligomer,monomer or additive should be included in the urethane concentrationcalculation. Examples of common monomers containing urethane linkagesinclude:

[0337] trimethylolpropane triacrylate,

[0338] the triacrylate or methacrylate from hexane-2,4,6

[0339] triol, or from glycerol, ethoxylated glycerol, or propoxylatedglycerol,

[0340] hexanediol diacrylate,

[0341] 1,3-butylene glycol diacrylate,

[0342] neopentyl glycol diacrylate,

[0343] 1,6-hexanediol diacrylate,

[0344] neopentyl glycol diacrylate,

[0345] polyethylene glycol-200 diacrylate,

[0346] tetraethylene glycol diacrylate,

[0347] triethylene glycol diacrylate,

[0348] pentaerythritol tetraacrylate,

[0349] tripropylene glycol diacrylate,

[0350] ethoxylated bisphenol-A diacrylate,

[0351] trimetylolpropane diacrylate,

[0352] di-trimethylolpropane tetraacrylate,

[0353] triacrylate of tris(hydroxyethyl) isocyanurate, dipentaerythritolhydroxypentaacrylate,

[0354] pentaerythritoltriacrylate,

[0355] ethoxylated trimethylolpropane triacrylate,

[0356] triethylene glycol dimethacrylate,

[0357] ethylene glycol dimethacrylate,

[0358] tetraethylene glycol dimethacrylate,

[0359] polyethylene glycol-2000 dimethacrylate,

[0360] 1,6-hexanediol dimethacrylate,

[0361] neopentyl glycol dimethacrylate,

[0362] polyethylene glycol-600 dimethacrylate,

[0363] 1,3-butylene glycol dimethacrylate,

[0364] ethoxylated bisphenol-A dimethacrylate, trimethylolpropanetrimethacrylate,

[0365] diethylene glycol dimethacrylate,

[0366] 1,4-butanediol diacrylate,

[0367] diethylene glycol dimethacrylate,

[0368] pentaerythritol tetramethacrylate,

[0369] glycerin dimethacrylate,

[0370] trimethylolpropane dimethacrylate,

[0371] pentaerythritol trimethacrylate,

[0372] pentaerythritol dimethacrylate,

[0373] pentaerythritol diacrylate, and

[0374] the like and mixtures thereof.

[0375] Mono(meth)acrylates such as cyclohexyl(meth)acrylate,

[0376] isobornyl(meth)acrylate,

[0377] lauryl(meth)acrylate,

[0378] alkoxylated phenolacrylate,

[0379] isooctyl-acrylate,

[0380] 2-ethylhexyl-acrylate,

[0381] hydroxyethyl acrylate, and

[0382] tetrahydrofurfuryl(meth)-acrylate.

[0383] (F) Ribbon Assemblies

[0384] Ribbon assemblies are now well known in the art and one skilledin the art will readily be able to use the disclosure provided herein toprepare the novel ribbon assemblies having enhanced ribbon strippabilityfor the desired applications. The novel ribbon assembly made accordingto this invention can be advantageously used in varioustelecommunication systems. Such telecommunication systems typicallyinclude ribbon assemblies containing optical glass fibers, incombination with transmitters, receivers, and switches. The ribbonassemblies containing the coated optical glass fibers are thefundamental connecting units of telecommunication systems. The ribbonassembly can be buried under ground or water for long distanceconnections, such as between cities. The ribbon assembly can also beused to connect directly to residential homes.

[0385] The novel ribbon assembly made according to this invention canalso be used in cable television systems. Such cable television systemstypically include ribbon assemblies containing optical glass fibers,transmitters, receivers, and switches. The ribbon assemblies containingthe coated optical glass fibers are the fundamental connecting units ofsuch cable television systems. The ribbon assembly can be buried underground or water for long distance connections, such as between cities.The ribbon assembly can also be used to connect directly to residentialhomes.

[0386] The novel ribbon assemblies can also be used in a wide variety oftechnologies, including but not limited to, various security systems,data transmission lines, high density television, and computer appliancesystems. It will be appreciated that as a result of the fundamentaldiscoveries described herein including the relationship between thefiber friction forces and the cohesive strength of the coatingsthemselves, and the means to control and establish such features andfunctions, the optical fiber art is now able to realize significantadvantages. These are primarily exhibited, as explained above, in thestripping and cable splicing function, but those operations arenonetheless critical in the establishment of a ribbon/cable network ofcommunication.

[0387] While the invention has been described in detail and withreference to specific embodiments thereof, it will be apparent to thoseof ordinary skill in the art that various changes and modifications canbe made to the claimed invention without departing from the spirit andscope thereof. For instance, while this invention has principally beendescribed with reference to ribbon constructions and assemblies ofoptical fibers, it is equally adaptable to other geometric andstructural arrays of multiple fiber conduits and cables.

[0388] (G) Ribbon Assembly Examples

[0389] Preparation of Inner Primary Coatings IP-1 and IP-2

[0390] The components shown in Table A.1 were combined to form differentinner primary coating compositions. The tests results for thesecompositions are also set forth in Table A.1 compositions. TABLE A.1Component (wt. %) IP-1 IP-2 Urethane Oligomer H-(I-PTGL-2000)₂-I-H 50.3050.40 Ethoxylated Nonylphenol Acrylate Ester 15.10 15.10 Phenoxy EthylAcrylate 20.00 20.00 Isobornyl Acrylate 10.00 10.002,4,6-Trimethylbenzoyl Diphenyl Phosphine 3.00 3.00 Oxide (Lucerin TPO)Thiodiethylene bis (3,5-di-tert-butyl-4-Hydroxy) 0.50 0.50Hydrocinnamate (Irganox 1035) γ-Mercaptopropyl Trimethoxy Silane (A-189)1.00 1.00 Silicone Fluid (Byk333) 0.10 0.00 Test Results Viscosity(mPa-s) 7500 7520 Tensile Strength (MPA) 1.1 0.9 Elongation (%) 277 239Secant Modulus (MPa) (measured on Mylar) 1.2 1.4 E′ = 1000 MPa, ° C.−50.5 −53.3 E′ = 100 MPa, ° C. −26.4 −29.1 Peak TAN Delta ° C. (Tg) −17−15.1 E₀, MPa 1.28 1.09 Adhesion at 50% RH (g/in) 41 40 Adhesion at 95%RH (g/in) 28 29 Crack Propagation (mm) 2.1 2 Fiber Friction (g/mm) 18.525

[0391] Preparation of Outer Primary Coatings OP-1 to OP-4

[0392] a.) Preparation of Oligomer 1

[0393] An oligomer composition, herein referred to as oligomer 1, wasprepared by adding 81.26 parts Adiprene L-200C, an isocyanate derivedfrom polypropyleneoxide diol having an average molecular weight of 1000reacted with toluene diisocyanate, to a reactor heated to 60° C. Thecontents of the reactor were mixed with a mechanical mixer operating atabout 100 rpm. 0.10 parts of butylated hydroxytoluene and 0.10 parts ofdibutyl tin dilaurate are admixed to the reactor contents. A blanket ofair @ 3 m³/hour is introduced into the reactor. Over a 1 hour period,18.54 parts of hydroxy ethyl acrylate was steadily introduced at rate sothe temperature did not exceed 70° C. The reactor contents weremaintained under these conditions for about 1 hour until the %NCO dropsbelow 0.2.

[0394] b) Preparation of Oligomer 2

[0395] An oligomer composition, herein referred to as oligomer 2, wasprepared by introducing 18.86 parts Olin TDI-90, a toluene diisocyanate,into a water jacketed reactor. The water jacket was controlled tomaintain the contents of the reactor at about 11° C. Then, 0.08 parts ofbutylated hydroxytoluene was added. The contents of the reactor werecontinually mixed with a mechanical mixer under an air sparge @ 3m³/hour. 15.01 parts of hydroxyethyl acrylate was steadily introduced atrate so the temperature did not exceed 60° C. The reactor contents weremaintained under these conditions for about 2 hours until the %NCOdropped below about 12. The reactor was then heated to 50° C. and 43.67parts PTG-L 1000 and 0.04 parts Crystalline DABCO(1,4-diazabicylo-[2,2,2]-octane) with the crystals pre-dissolved in aportion of the PTG-L 1000(polymethyltetrahydrofurfuryl/polytetrahydrofurfuryl copolymer diolhaving a molecular weight of 1,000 (Mitsui, N.Y.)), were introduced. Thereactor temperature was then increased to 80° C. and maintained therefor about 90 minutes until the NCO% dropped below 0.2.

[0396] Table A.2 sets forth the outer primary coating compositions byweight percent of component introduced to form the composition andmeasured properties of the respective outer primary compositions. TABLEA.2 Components (wt. %) OP-1 OP-2 OP-3 OP-4 Oligomer 1 36 38.6 Oligomer 221.67 Oligomer 58 CN-120 Epoxy Acrylate (Sartomer) 28.7 Bis-Phenol AEthoxylated Diacrylate 11 Isobornyl Acrylate 12 9.8 Phenoxy EthylAcrylate 6.1 9.5 Ethoxylated₃.Bisphenol A Diacrylate (SR-349) 58 56Ethoxylated₄ Nonylphenol Acrylate Ester (SR- 3.5 13.84 504A)Bis(1,2,2,6,6-tetramethyl-4-piperidinyl) Sebacate 0.5 (Tinuvin 292)Triethylene Glycol bis[3,3′(t-butyl-4-hydroxy-5- 0.5 0.5methylphenyl)propionate] (Irganox 245) Vinyl Caprolactam 8.52,4,6-Trimethylbenzoyl Diphenyl Phosphine 2.0 2.43 1 1.5 Oxide (LucerinTPO) 1-Hydroxycyclohexyl Phenyl Ketone (Irgacure 4.85 2 1 184)Thiodiethylene bis (3,5-di-tert-butyl-4-Hydroxy) 1.21 0.3 Hydrocinnamate(Irganox 1035) Dow Corning Silicone/Silane Additive - 57 0.4 0.7 DowCorning Surfactant 190 0.7 1.3 Test Results Viscosity (mPa-s) 9000 7700Tensile Strength (MPA) 28 26 Elongation (%) 10 13 22 7 Secant Modulus(MPa) (tested on mylar) 1100-1200 800-850 900 910

[0397] Ribbon Preparation (Coating System and Ink Coating)

EXAMPLE 1-3 Comparative Examples 1-9

[0398] 125±μm optical fibers were prepared from F-300 Suprasil Preform(Heraeus) in a draw tower. The draw tower line speed was maintained at aconstant speed of about 300 m/min for all experiments. Inner and outerprimary coating compositions of the particular coating system (SeeTables, above) were supplied to the primary and secondary coating feedsystems of the draw tower in 2 Kg bottles introduced into thepressurized pots. The pressurized pots were pressurized with high-purityair. The pressurized pots, transfer lines and coating dies for eachcoating feed system were heated with a dual water bath system (one bathfor the die and one for the pressurized pot and transfer line).

[0399] The inner primary coating was applied as the primary coating tothe fiber using a 215 μm Heathway inlet die and cured with a 300 wattFusion lamp fitted with a 9 mm D bulb. The process was controlled sothat the diameter of the coated fiber after application and cure of theprimary coating was 195±μm. Similarly, an outer primary coating wasapplied as a secondary coating about the primary coating using a 255 μmHeathway inlet die. The outer primary coating was cured with a 600 wattFusion lamp fitted with a 11 mm D bulb set at 50% power using a VPSpower supply and a second 300 watt Fusion lamp fitted with a 9 mm bulb.The exit dies for both the primary and secondary coating steps were 500μm.

[0400] A single matrix material composed of the ingredients set forth inthe following table was used for all ribbon assemblies.

[0401] In a subsequent procedure, the fiber was color coded with LTSinks (Desotech) in a nitrogen atmosphere at line speed 300 m/min andcured with a single 9 mm 300 watt/m D bulb. The color coded fibers werethen assembled into a ribbon, at a line speed of 60 m/min, by uniformlyapplying the matrix material, described in the following Table A.3,followed by curing it with a 11 mm D bulb curing lamp. Although severaldifferent color LTS inks were used, a single die having a 259 μmentrance diameter was used for all ink coatings to insure consistency.Similarly, each ribbon assembly step was performed using the same matrixmaterial and control parameters for the coating and curing steps tominimize the introduction of any inconsistencies.

[0402] A single matrix composed of the components shown in Table A.3were combined to form different inner primary coating compositions.TABLE A.3 Matrix Components (wt. %) Material Oligomer 1 39.57 IsobornylAcrylate 10.14 SR-238, 1,6 Hexanediol Diacrylate (Sartomer) 6.92 SR-339,2-Phenoxyethyl Acrylate (Sartomer) 9.89 CN-120 Epoxy Acrylate (Sartomer)29.43 Bis(1,2,2,6,6-tetramethyl-4-piperidinyl) Sebacate 0.5 (Tinuvin292) Triethylene Glycol bis[3,3′(t-butyl-4-hydroxy-5- 0.5methylphenyl)propionate] (Irganox 245) 2,4,6-Trimethylbenzoyl DiphenylPhosphine 2.03 Oxide (Lucerin TPO) Dow Corning Silicone/SilaneAdditive - 57 0.36 Dow Corning Surfactant 190 0.66

[0403] Table A.4 sets forth the inner and outer primary coatingsemployed in the coating system and the measured and average ribbonstripping values for the ribbon assembly. TABLE A.4 Coating SystemRating Per Inner Outer Stripping Average Example No. Primary Primary1^(st) 2^(nd) 3^(rd) 4^(th) Rating Example 1 IP-1 OP-1 2 2 3 3 2.25Comparative Example 1 IP-1 OP-2 4 4 5 5 4.5 Comparative Example 2 IP-1OP-3 4 4 5 5 4.5 Comparative Example 3 IP-1 OP-3 5 5 5 — 5 ComparativeExample 4 IP-1 OP-4 5 5 5 — 5 Comparative Example 5 IP-2 OP-1 4 5 4 44.25 Comparative Example 6 IP-2 OP-1 4 5 5 4 4.5 Comparative Example 7IP-2 OP-2 5 5 5 — 5 Comparative Example 8 IP-2 OP-2 5 5 5 — 5Comparative Example 9 IP-2 OP-3 5 5 5 — 5 Comparative Example 10 IP-2OP-3 5 5 5 — 5 Comparative Example 11 IP-2 OP-4 5 5 5 — 5

[0404] Comparative Examples 5 and 6 with a high modulus outer primarycoating composition stripped better than those with a relatively lowmodulus outer primary coating composition. And Comparative Examples 1-4on average, particularly Comparative Examples 1 and 2, with an innerprimary coating having a slip enhancing component stripped better thansimilar compositions, Comparative Examples 7-11, with inner primarycoatings having no slip enhancing component. However, Example 1, acoating system with a high modulus outer primary coating composition andan inner primary coating composition comprising a slip enhancingcomponent, provided a strip cleanliness value significantly better thanany of the various Comparative Examples.

[0405] (I) Description of Test Methods

[0406] (1) 60° C. Water Soak Delamination Test

[0407] Films of the coating materials (75 microns thick) were preparedon microscope slides and then cured by exposure to 1.0 J/sq cm, from aFusion D lamp, 120 W/cm, under a nitrogen atmosphere. A commerciallyavailable outer primary coating was drawndown and cured in a similarfashion on top of the coatings. Deionized water was placed in a 500 mlbeaker and the coated microscope slides were soaked in the water. Thebeaker containing the coated slides was then placed in a 60° C. hotwater bath. The films were observed for delamination periodically. Thetime when the first signs of delamination appeared were recorded.

[0408] (2) Fiber Pull-Out Residue Test

[0409] The operation of stripping coatings from optical fibers to leavea bare glass surface was simulated by pulling four bare glass fibers outof a layer of cured inner primary coating. Microscopic examination ofthe pulled-out fibers at low magnification (e.g., 10×) clearly revealedthe presence or absence of residue on the glass surface. If residue waspresent, the amount of residue was noted. The relative amount of residuedebris is sometimes rated on a scale of 0 to 10, where 0 is the best (novisible residue under 10×magnification) and 10 is the worst (lots ofvisible residue without use of magnification).

[0410] (3) Viscosity Test Method

[0411] The viscosity was measured using a Physica MC10 Viscometer. Thetest samples were examined and if an excessive amount of bubbles waspresent, steps were taken to remove most of the bubbles. Not all bubblesneed to be removed at this stage, because the act of sample loadingintroduces some bubbles.

[0412] The instrument was set up for the conventional Z3 system, whichwas used. The samples were loaded into a disposable aluminum cup byusing the syringe to measure out 17 cc. The sample in the cup wasexamined and if it contains an excessive amount of bubbles, they wereremoved by a direct means such as centrifugation, or enough time wasallowed to elapse to let the bubbles escape from the bulk of the liquid.Bubbles at the top surface of the liquid are acceptable.

[0413] The bob was gently lowered into the liquid in the measuring cup,and the cup and bob were installed in the instrument. The sampletemperature was allowed to equilibrate with the temperature of thecirculating liquid by waiting five minutes. Then, the rotational speedwas set to a desired value which will produce the desired shear rate.The desired value of the shear rate is easily determined by one ofordinary skill in the art from an expected viscosity range of thesample.

[0414] The instrument panel read out a viscosity value, and if theviscosity value varied only slightly (less than 2% relative variation)for 15 seconds, the measurement was complete. If not, it is possiblethat the temperature had not yet reached an equilibrium value, or thatthe material was changing due to shearing. If the latter case, furthertesting at different shear rates will be needed to define the sample'sviscous properties. The results reported are the average viscosityvalues of three test samples.

[0415] (4) Tensile Strength, Elongation and Modulus Test Method

[0416] The tensile strength, elongation and secant modulus of curedsamples was tested using a universal testing instrument, Instron Model4201 equipped with a personal computer and software “Series IX MaterialsTesting System.” The load cells used were 2 and 20 pound capacity. TheASTM D638M was followed, with the following modifications.

[0417] A drawdown of each material to be tested was made on glass plateor Mylar (in particular, the outer primary coating compositions, unlessotherwise noted, were measured on Mylar) and cured using a UV processor.The cured film was conditioned at 22 to 24° C. and 50±5% relativehumidity for a minimum of sixteen hours prior to testing.

[0418] A minimum of eight test specimens, having a width of 0.5±0.002inches and a length of 5 inches, were cut from the cured film. Tominimize the effects of minor sample defects, sample specimens were cutparallel to the direction in which the drawdown of the cured film wasprepared. If the cured film was tacky to the touch, a small amount oftalc was applied to the film surface using a cotton tipped applicator.

[0419] The test specimens were then removed from the substrate. Cautionwas exercised so that the test specimens were not stretched past theirelastic limit during the removal from the substrate. If any noticeablechange in sample length had taken place during removal from thesubstrate, the test specimen was discarded.

[0420] If the top surface of the film was talc coated to eliminatetackiness, then a small amount of talc was applied to the bottom surfaceof test specimen after removal from the substrate.

[0421] The average film thickness of the test specimens was determined.At least five measurements of film thickness were made in the area to betested (from top to bottom) and the average value used for calculations.If any of the measured values of film thickness deviates from theaverage by more than 10% relative, the test specimen was discarded. Allspecimens came from the same plate.

[0422] The appropriate load cell was determined by using the followingequation:

[A×145]×0.0015=C

[0423] Where:

[0424] A=Product's maximum expected tensile strength (MPa);

[0425] 145=Conversion Factor from MPa to psi;

[0426] 0.00015=approximate cross-sectional area (in²) of test specimens;and

[0427] C=lbs.

[0428] The 2 pound load cell was used for materials where C=1.8 lbs. The20 pound load cell was used for materials where 1.8<C<18 lbs. If C>19, ahigher capacity load cell was required.

[0429] The crosshead speed was set to 1.00 inch/min (25.4 mm/min), andthe crosshead action was set to “return at break”. The crosshead Wasadjusted to 2.00 inches (50.8 mm) jaw separation. The air pressure forthe pneumatic grips was turned on and adjusted as follows: setapproximately 20 psi (1.5 Kg/cm²) for primary optical fiber coatings andother very soft coatings; set approximately 40 psi (3 Kg/cm²) foroptical fiber single coats; and set approximately 60 psi (4.5 Kg/cm²)for secondary optical fiber coatings and other hard coatings. Theappropriate Instron computer method was loaded for the coating to beanalyzed.

[0430] After the Instron test instrument had been allowed to warm-up forfifteen minutes, it was calibrated and balanced following themanufacturer's operating procedures.

[0431] The temperature near the Instron Instrument was measured and thehumidity was measured at the location of the humidity gage. This wasdone just before beginning measurement of the first test specimen.

[0432] Specimens were only analyzed if the temperature was within therange 23±1.0 C. and the relative humidity was within 50±5%. Thetemperature was verified as being within this range for each testspecimen. The humidity value was verified only at the beginning and theend of testing a set of specimens from one plate.

[0433] Each test specimen was tested by suspending it into the spacebetween the upper pneumatic grips such that the test specimen wascentered laterally and hanging vertically. Only the upper grip waslocked. The lower end of the test specimen was pulled gently so that ithas no slack or buckling, and it was centered laterally in the spacebetween the open lower grips. While holding the specimen in thisposition, the lower grip was locked.

[0434] The sample number was entered and sample dimensions into the datasystem, following the instructions provided by the software package.

[0435] The temperature and humidity were measured after the last testspecimen from the current drawdown was tested. The calculation oftensile properties was performed automatically by the software package.

[0436] The values for tensile strength, % elongation, and secant, orsegment, modulus were checked to determine whether any one of themdeviated from the average enough to be an “outlier.” If the modulusvalue was an outlier, it was discarded. If there were less than six datavalues for the tensile strength, then the entire data set was discardedand repeated using a new plate.

[0437] (5) Dynamic Mechanical Testing

[0438] The elastic modulus (E′), the viscous modulus (E″), and the tandelta (E″/E′), which is an indication of the material's Tg, of theexamples were measured using a Rheometrics Solids Analyzer (RSA-11),equipped with: 1) a personal computer having MS-DOS 5.0 operating systemand having Rhios® software (Version 4.2.2 or later) loaded, and 2) aliquid nitrogen controller system for low-temperature operation.

[0439] The test samples were prepared by casting a film of the material,having a thickness in the range of 0.02 mm to 0.4 mm, on a glass plate.The sample film was cured using a UV processor. A specimen approximately35 mm (1.4 inches) long and approximately 12 mm wide was cut from adefect-free region of the cured film. For soft films, which tend to havesticky surfaces, a cotton-tipped applicator was used to coat the cutspecimen with talc powder.

[0440] The film thickness of the specimen was measured at five or morelocations along the length. The average film thickness was calculated to±0.001 mm. The thickness cannot vary by more than 0.01 mm over thislength. Another specimen was taken if this condition was not met. Thewidth of the specimen was measured at two or more locations and theaverage value calculated to ±0.1 mm.

[0441] The geometry of the sample was entered into the instrument. Thelength field was set at a value of 23.2 mm and the measured values ofwidth and thickness of the sample specimen were entered into theappropriate fields.

[0442] Before conducting the temperature sweep, moisture was removedfrom the test samples by subjecting the test samples to a temperature of80 C. in a nitrogen atmosphere for 5 minutes. The temperature sweep usedincluded cooling the test samples to about −60 C. or about −80 C. andincreasing the temperature at about 1 /minute until the temperaturereached about 60 C. to about 70 C. The test frequency used was 1.0radian/second.

[0443] (6) Crack Propagation

[0444] The crack propagation is measured as follows. First a specimen isprepared by of 75 micron thick drawdown of the subject composition andthen cured to form a film by exposing it to 1.0 J/cm² of UV from aFusion D lamp under a nitrogen atmosphere. Cut three test strips ofdimensions 35 mm long, 12 mm wide, and 75 micron thick. A cut 2.5 mmlong is made in the side of each strip. A strip is mounted in a RSA-IIrheometer, the temperature brought to 90° C. (representative ribbonstripping temperature), and a constant extension rate of 0.1 mm/secondis applied to the test strip. The crack propagation value is theincrease in length L before the crack propagates across the width of thetest strip. The gauge length is constant at 23.2 mm. The value reportedis typically an average of three measurements.

[0445] (7) Fiber Pull-Out Friction

[0446] The fiber pull-out friction test can be performed as follows. Thesample consists of a bare, clean optical fiber, one end of which hasbeen embedded in a 250 micron thick sheet of cured inner primary coatingto be tested. This assembly is mounted in a suitable instrument such asa Rheometrics RSA-II rheometer, and the temperature raised to arepresentative ribbon stripping temperature (such as 90° C.), and thefiber pulled slowly out of the sheet at a rate of 0.1 mm/sec. Theinstrument records and plots force vs. distance. The plots typicallyshow a linear region of negative slope, which is the result of adecreasing area of contact between fiber and coating, as the fiber isbeing withdrawn. The slope is measured, and is the output of the test.Low slope values correspond to a low fiber pull-out friction, and viceversa. Three test samples should be performed and their average used asthe final output of the test.

[0447] The fiber pull-out friction of the inner primary coating is anestimate of the fiber friction between the inner primary coating and thebare optical glass fiber. In general, the lower the fiber pull-outfriction of the inner primary coating the lower the fiber frictionbetween the optical glass fiber and the inner primary coating, the lowerthe resistive force, and the easier the inner primary coating will slideoff of the optical glass fiber. Also, the lower the fiber friction, theless force that will be applied to the inner primary coating to conductribbon stripping. The less the force being applied to the inner primarycoating, the lower the chance that the cohesiveness of the inner primarycoating will fail, thus leaving inner primary coating residue on thesurface of the optical glass fiber.

[0448] (8) Dry (50% RH) and Wet (95% RH) Adhesion

[0449] Dry 50% RH) and wet (95% RH) adhesion can be measured byrecognized test methods. For example, as explained in U.S. Pat. No.5,336,563 (Coady et al.) and U.S. Pat. No. 5,384,342 (Szum), the wet anddry adhesion was tested on cured film samples prepared by drawing down,with a Bird Bar, a 75 micron film of the coating compositions on glassmicroscope slides and cured by exposure to 1.0 J/sq cm, from a Fusion Dlamp, 120 W/cm, under a nitrogen atmosphere.

[0450] The samples were then conditioned at a temperature of 23±2° C.and a relative humidity of 50±5% for a time period of 7 days. A portionof the film was utilized to test dry adhesion. Subsequent to dryadhesion testing, the remainder of the film to be tested for wetadhesion was further conditioned at a temperature of 23±2° C. and arelative humidity of 95% for a time period of 24 hours. A layer ofpolyethylene wax/water slurry was applied to the surface of the furtherconditioned film to retain moisture.

[0451] The adhesion test was performed utilizing apparatus whichincluded a universal testing instrument, e.g., an Instron Model 4201commercially available from Instron Corp., Canton, Mass., and a device,including a horizontal support and a pulley, positioned in the testinginstrument.

[0452] After conditioning, the samples that appeared to be uniform andfree of defects were cut in the direction of the draw down. Each samplewas 6 inches long and 1 inch wide and free of tears or nicks. The firstone inch of each sample was peeled back from the glass. The glass wassecured to the horizontal support with the affixed end of the specimenadjacent the pulley. A wire was attached to the peeled-back end of thesample, run along the specimen and then run through the pulley in adirection perpendicular to the specimen. The free end of the wire wasclamped in the upper jaw of the testing instrument which was thenactivated. The test was continued until the average force value, ingrams force/inch, became relatively constant. A suitable value for wetadhesion is at least about 5 g/in, preferably at least about 10 g/in,and more preferably at least about 15 g/in when conditioned at 95% (RH).

[0453] (9) Ribbon Stripping Test Procedure

[0454] A ribbon sample, prepared as described above, was preconditionedfor 2 hours in a 25° C., 48% relative humidity, environment. A 30 mm±3mm portion was manually stripped from each ribbon sample using aSumitomo Stripping Tool, Model #JR-4A, set at a heating temperature of100° C. and using a 5 second dwell time. Dwell time is defined as thetime from closure of the stripping tool about the specimen until astripping force is imposed. To insure reliability, a minimum of threestrip procedures were performed on each sample. If there was anydifference in the values in the first three strip procedures, a fourthstrip procedure was performed. After each ribbon stripping procedure,the fibers were evaluated for cleanliness and fiber integrity inaccordance with the following rating system. Once the rating value wasrecorded, the stripped portion of the sample was removed by cutting theribbon thereby presenting a virgin portion for subsequent stripprocedures. Rating Evaluation Criteria 1 Matrix and coating materialsstripped off as one piece with no residue visible on the fiber. 2 Matrixand/or coating materials crumble or break up leaving a slight residue onfiber with no residue visible on the fiber after one wipe with anorganic solvent. 3 Matrix and/or coating materials crumble or break upleaving a moderate residue on fiber with no residue visible on the fiberafter one wipe with an organic solvent. 4 Matrix and/or coatingmaterials crumble or break up leaving a heavy residue on fiber with someresidue visible on fiber after one wipe with an organic solvent. 5Incomplete strip, some fiber coating remains intact.

[0455] Although the present invention has been described and illustratedin detail, it should be clearly understood that the same is by way ofillustration and example only and is not to be taken by way oflimitation, the spirit and scope of the present invention being limitedonly by the terms of the claims appended hereto.

What is claimed is:
 1. A system for coating an optical glass fibercomprising a radiation-curable inner primary coating composition and aradiation-curable outer primary coating composition wherein: saidradiation-curable inner primary coating composition comprising at leastone strip enhancing component, said inner primary coating composition,after radiation cure, having the combination of properties of: (a) aglass transition temperature of below 0° C.; and (b) adhesion to glassof at least 5 g/in when conditioned at 95% relative humidity; and saidouter primary coating composition comprising an oligomer having at leastone functional group capable of polymerizing under the influence ofradiation, said outer primary coating composition, after radiation cure,having a secant modulus of greater than 1000 MPa at 23° C.
 2. A coatedoptical glass fiber, coated with at least an inner primary coating andan outer primary coating, wherein said inner primary coating is derivedfrom a composition comprising an oligomer having at least one functionalgroup capable of polymerizing under the influence of radiation and an atleast one strip enhancing component, said inner primary coating having:(a) a glass transition temperature of below 0° C.; and (b) adhesion toglass of at least 5 g/in when conditioned at 95% relative humidity; andsaid outer primary coating having a secant modulus of greater than 1000MPa at 23° C.
 3. A ribbon assembly comprising: a plurality of coatedoptical glass fibers, at least one optical glass fiber coated with atleast an inner primary coating and an outer primary coating, andoptionally an ink coating; and a matrix material bonding said pluralityof coated optical glass fibers together, wherein: said inner primarycoating derived from a composition comprising an oligomer having atleast one functional group capable of polymerizing under the influenceof radiation and an at least one strip enhancing component, said innerprimary coating having: (a) a glass transition temperature of below 0°C.; and (b) adhesion to glass of at least 5 g/in when conditioned at 95%relative humidity; and said outer primary coating having a secantmodulus of greater than 1000 MPa at 23° C.
 4. The system of claim 1wherein said slip enhancing component is a composite oligomercomprising: at least one glass coupling moiety; at least one slip agentmoiety; and at least one radiation-curable moiety.
 5. The system ofclaim 1 wherein said slip enhancing component includes a soluble waxand/or a solid lubricant.
 6. The system of claim 1 wherein said slipenhancing component includes a radiation-curable silicone oligomercomprising: a silicone compound; and at least one radiation-curablemoiety and/or a non-radiation-curable silicone compound.
 7. The systemof claim 1 wherein said slip enhancing component is a fluorinatedcomponent selected from the group consisting of a radiation-curablefluorinated oligomer, a radiation-curable fluorinated monomer and anon-radiation curable fluorinated compound.
 8. The system of claim 1wherein said slip enhancing component is a radiation-curable oligomercomprising: at least one terminal linear moiety.
 9. The system of claim1 wherein said slip enhancing component is a solid lubricant.
 10. Thesystem of claim 1 wherein said slip enhancing component is asubstantially linear radiation-curable oligomer.
 11. The system of claim1 wherein said slip enhancing component includes a low-urethane contentoligomer present in an amount such that the urethane concentration ofurethane groups present in said inner primary coating composition isabout 3.5% by weight or less.
 12. The system of claim 1 wherein saidslip enhancing component is a high molecular weight polymeric oligomercomprising a polymeric block having a molecular weight of at least about3000.
 13. The system of claim 1 wherein said slip enhancing componentincludes a high aromatic oligomer and/or monomer diluent.
 14. The systemof claim 1 wherein said slip enhancing component is a silicone compoundterminated with at least one radiation-curable functional group.
 15. Thesystem of claim 1 wherein said slip enhancing component is a fluorinatedcomponent selected from the group consisting of a radiation-curablefluorinated oligomer, a radiation-curable fluorinated monomer and anon-radiation curable fluorinated compound.
 16. The system of claim 1wherein said slip enhancing component is a silicone-component selectedfrom the group consisting of a radiation-curable silicone oligomer, aradiation-curable silicone monomer and a radiation-curable siliconecompound and a non-radiation curable silicone compound.
 17. The systemof claim 1 wherein said slip enhancing component is a solid lubricant.18. The system of claim 1 wherein said inner primary coatingcomposition, after cure, has a crack propagation of greater than 0.7 mmat 90° C. and a fiber pull-out friction of less than 40 g/mm.
 19. Thesystem of claim 18 wherein said inner primary coating composition, aftercure, has a Tg of less than −10° C. and said outer primary coatingcomposition, after cure, has a Tg of greater than 40° C.
 20. The systemof claim 19 wherein said inner and outer primary coating compositionseach comprise a radiation-curable urethane acrylate oligomer and atleast one acrylate monomer.